Composition including material, methods of depositing material, articles including same and systems for depositing material

ABSTRACT

Methods for depositing nanomaterial onto a substrate are disclosed. Also disclosed are compositions useful for depositing nanomaterial, methods of making devices including nanomaterials, and a system and devices useful for depositing nanomaterials.

This application is a continuation of commonly owned PCT Application No.PCT/US2007/008873 filed 9 Apr. 2007, which was published in the Englishlanguage as PCT Publication No. WO 2007/117698 on 18 Oct. 2007. The PCTApplication claims priority from commonly owned U.S. Application Nos.60/790,393 filed 7 Apr. 2006; 60/792,170 filed 14 Apr. 2006; and60/792,086 filed 14 Apr. 2006. The disclosures of each of theseapplications are hereby incorporated herein by reference in theirentireties.

TECHNICAL FIELD OF THE INVENTION

The invention relates to compositions and methods of depositing same.More particularly, the invention relates to compositions includingnanomaterial, methods and systems for depositing same.

BACKGROUND OF THE INVENTION

A number of industries, e.g., electronics, displays, lighting,optoelectronics, and energy industries, rely on the formation of layers,coatings and/or patterns of materials to form pixels, circuits, andother features on substrates. The primary methods for generating thesepatterns are screen printing for features larger than about 100 micronsand thin film and etching methods for features smaller than about 100microns. Other subtractive methods to attain fine feature sizes includethe use of photo-patternable pastes and laser trimming.

SUMMARY OF THE INVENTION

It has been recognized that it would be advantageous to develop improvedmethods, systems, devices, and compositions for depositing nanomaterialsonto a substrate.

In accordance with one aspect of the invention, there is provided amethod for depositing nanomaterial onto a substrate. The method includesapplying a composition comprising nanomaterial to an applicator surfacefrom a transfer surface, and contacting the applicator surface to thesubstrate.

In accordance with a further aspect of the invention, there is provideda method for depositing nanomaterial onto a substrate. The methodincludes applying nanomaterial to an applicator surface from a transfersurface, and contacting the applicator surface to the substrate.

In accordance with another aspect of the invention, there is provided amethod for depositing nanomaterial onto a substrate. The method includesapplying a layer comprising nanomaterial to an applicator surface from atransfer surface, and contacting the applicator surface to thesubstrate. The layer applied to the applicator can be patterned orunpatterned.

In accordance with a still further aspect of the invention, there isprovided a method of depositing nanomaterial onto a substrate. Themethod includes applying a composition comprising nanomaterial and acarrier medium to a surface of an applicator from a transfer surface,and depositing at least a portion of the composition from the applicatoronto the substrate.

In accordance with a still further aspect of the invention, there isprovided a method for depositing a nanomaterial onto a substrate. Themethod comprises applying a composition comprising nanomaterial to anapplicator surface; positioning a mask including a predetermined patternof apertures comprising a predetermined shape and size on the substrate;and contacting the applicator surface to the substrate through at leasta one of the apertures.

In accordance with another aspect of the invention, there is provided amethod of depositing nanomaterial onto a substrate. The method includesintroducing a composition comprising nanomaterial and liquid onto atransfer surface; transferring at least a portion of the compositionfrom the transfer surface onto an applicator; removing at least aportion of the liquid from the composition; and depositing at least aportion of the at least partially liquid-free composition from theapplicator onto the substrate.

In accordance with another aspect of the invention, there is provided amethod of depositing nanomaterial onto a substrate. The method includesintroducing a composition comprising nanomaterial and liquid onto atransfer surface; removing at least a portion of the liquid from thecomposition; transferring at least a portion of at least partiallyliquid-free composition from the transfer surface onto an applicator;and depositing at least a portion of the at least partially liquid-freecomposition from the applicator onto the substrate.

In accordance with a further aspect of the invention, there is provideda method for depositing nanomaterial onto a substrate. The methodcomprises introducing a composition comprising nanomaterial onto atransfer surface, and contacting a surface of the substrate with thetransfer surface, and separating the substrate from the transfersurface.

In accordance with another aspect of the invention, there is provided amethod of making a light emitting device. The method comprises applyinga composition comprising semiconductor nanocrystals to an applicatorsurface from a transfer surface; and contacting the applicator surfaceto a substrate.

In accordance with another aspect of the invention, there is provided amethod of forming a device comprising applying nanomaterial to a surfaceof an applicator from a transfer surface, contacting the surface of theapplicator to a substrate including a first electrode, therebytransferring at least a portion of the nanomaterial onto the substrate;and arranging a second electrode opposed to the first electrode.

In accordance with yet another aspect of the invention, there isprovided a system for depositing nanomaterial onto a substrate. Thesystem comprises a transfer surface; means for dispensing a compositioncomprising nanomaterial onto the transfer surface, and means fordepositing the composition from the transfer surface onto the substrate.

In accordance with yet another aspect of the invention, there isprovided a composition useful for depositing nanomaterial onto asubstrate. The composition includes nanomaterial. The composition canfurther include a carrier medium (e.g., liquid). Optionally, thecomposition can further include one or more additional components. Incertain embodiments, nanomaterial comprises nanoparticles. Examples ofnanoparticles include, for example, a semiconductor nanocrystal, ananotube (such as a single walled or multi-walled carbon nanotube), ananowire, a nanorod, a dendrimer, organic nanocrystal, organic smallmolecule, other nano-scale or micro-scale material or mixtures thereof.

In accordance with yet another aspect of the invention, there isprovided an applicator made from a material comprising a silicon basedelastomer (e.g., without limitation, PDMS) doped with a fluorinatedpolymer. In certain embodiments, the fluorinated polymer is included inthe material in an amount greater than zero up to at least about 0.1weight percent. In certain other embodiments, the fluorinated polymercan be included in an amount of at least about 0.001 weight percent. Theamount of fluorinated polymer dopant can be included in the stampmaterial up to an amount that is less than the amount at which thesilicon based elastomer including the fluorinated polymer dopant cannotbe cured (e.g., forms an uncurable gel). In certain embodiments, thefluorinated polymer dopant comprises a fluorinated polysiloxane.

Other aspects of the invention include further articles and methodsincluding deposited nanomaterial, systems, and devices for depositingcompositions comprising nanomaterials.

The foregoing, and other aspects described herein all constituteembodiments of the present invention.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the invention as claimed. Other embodimentswill be apparent to those skilled in the art from consideration of thespecification and practice of the invention disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIGS. 1A-B are diagrams depicting examples of an embodiment of atransfer surface including a pattern of grooves.

FIGS. 2 A-B are diagrams depicting examples of embodiments including amask.

FIGS. 3 A-B are diagrams depicting an example of a method for depositingone or more compositions and/or nanomaterials onto a substrate.

FIG. 4 is a diagram depicting an example of a technique for dispensingone or more compositions to a transfer surface.

FIG. 5 illustrates an example of a technique for dispensing one or morecompositions to a transfer surface.

FIGS. 6 A-D illustrate diagrams depicting an example of a method fordepositing one or more compositions and/or nanomaterials onto asubstrate.

FIG. 7 is a diagram depicting an example of a method of the inventionincluding a tape.

FIG. 8 are diagrams depicting examples of applicators for use in variousembodiments of a method of the invention.

FIG. 9 is diagram depicting an example of a system for use in variousembodiments of a method of the invention.

FIGS. 10 A-D are diagrams depicting an example of a system including atransfer surface and tape for use in various embodiments of a method ofthe invention.

FIG. 11 is a diagram depicting an example of a system including a tapefor use in various embodiments of a method of the invention.

FIG. 12 is a diagram depicting an example of a system including atransfer surface and applicator for use in various embodiments of amethod of the invention.

FIG. 13 is a schematic drawing depicting a light-emitting device.

The attached figures are simplified representations presented forpurposed of illustration only; the actual structures may differ innumerous respects, including, e.g., relative scale, etc.

For a better understanding to the present invention, together with otheradvantages and capabilities thereof, reference is made to the followingdisclosure and appended claims in connection with the above-describeddrawings.

DETAILED DESCRIPTION OF THE INVENTION

One aspect of the invention relates to methods for depositingnanomaterial onto a substrate.

The nanomaterial can optionally be included in a composition. Thecomposition can further include a liquid or other carrier medium. Thecomposition can further include one or more additional components.

A nanomaterial typically includes nanoparticles having an averagemaximum dimension smaller than 100 nm.

Examples of nanoparticles include, for example, semiconductornanocrystal, a nanotube (such as a single walled or multi-walled carbonnanotube), a nanowire, a nanorod, a dendrimer, organic nanocrystal,organic small molecule, other nano-scale or micro-scale material ormixtures thereof.

Nanomaterial particles can have various shapes, including, but notlimited to, sphere, rod, disk, other shapes, and mixtures of variousshaped particles.

Examples of organic nanocrystals include, without limitation,J-aggregates, H-aggregates, and organic nanocrystals includingaggregates with other dipole arrangements. Examples of organicnanocrystals are described in S. Kirstein et al., “HerringboneStructures In Two-Dimensional Single Crystals of Cyanine Dyes. I.Detailed Structure Analysis Using Electron Diffraction”, J. Chem. Phys.103(2) July 1995, pages 816 et seq.; S. Kirstein et al., “HerringboneStructures In Two-Dimensional Single Crystals of Cyanine Dyes. II.Optical Properties”, J. Chem. Phys. 103(2) July 1995, pages 826 et seq.;A. Mishra et al. “Cyanines During the 1990s: A Review”, Chem. Rev. 2000,100, 1973-2011; and C. Peyratout et al., “Aggregation of ThiacyanineDerivatives On Polyelectrolytes:, Phys. Chem. Chem. Phys., 2002, 4,3032-3039, the disclosures of which are hereby incorporated herein byreference in their entireties.

The present invention will be useful for depositing nanomaterials,including, but not limited to, nanomaterials with optical and/orelectronic characteristics, in patterned or unpatterned arrangements.

A nanomaterial can include one nanomaterial or a mixture of two or moredifferent nanomaterials. Nanomaterials can be different based on, e.g.chemical composition, particle morphology (e.g., size, shape, surfacearea, particle size distribution, Full Width at Half-Maximum (FWHM),etc.), surface treatment(s) (e.g., not surface-modified, surfacemodified, and if surface modified, the details of the surfacemodification (e.g., composition, etc.)), particle structure (e.g.,uncoated or coated; and if coated, the details of the coating, e.g.,composition, thickness, nature of the coating (e.g., continuous,non-continuous, particulate, film, etc.)), performance characteristics(e.g., absorption properties, emission characteristics, etc.) of eachnanomaterial, different combinations of chemical, physical, and/orperformance aspects, etc.

In certain embodiments, nanomaterial includes semiconductornanocrystals. Semiconductor nanocrystals comprise nanometer-scaleinorganic semiconductor particles. Semiconductor nanocrystals preferablyhave an average nanocrystal diameter less than about 150 Angstroms

and most preferably in the range of 12-150

In certain embodiments, inorganic semiconductor nanocrystals compriseGroup IV elements, Group II-VI compounds, Group II-V compounds, GroupIII-VI compounds, Group III-V compounds, Group IV-VI compounds, GroupI-III-VI compounds, Group II-IV-VI compounds, or Group II-IV-Vcompounds, alloys thereof and/or mixtures thereof, including ternary andquaternary alloys and/or mixtures. Examples include, but are not limitedto, ZnO, ZnS, ZnSe, ZnTe, CdO, CdS, CdSe, CdTe, HgO, HgS, HgSe, HgTe,AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, GaSe, InN, InP, InAs, InSb,TlN, TlP, TlAs, TlSb, PbO, PbS, PbSe, PbTe, alloys thereof, and/ormixtures thereof, including ternary and quaternary alloys and/ormixtures.

In certain embodiments, semiconductor nanocrystals preferably include a“core” of one or more first semiconductor materials, which may besurrounded by an overcoating or “shell” of a second semiconductormaterial. A semiconductor nanocrystal core surrounded by a semiconductorshell is also referred to as a “core/shell” semiconductor nanocrystal.

For example, the semiconductor nanocrystal can include a core having theformula MX, where M is cadmium, zinc, magnesium, mercury, aluminum,gallium, indium, thallium, or mixtures thereof, and X is oxygen, sulfur,selenium, tellurium, nitrogen, phosphorus, arsenic, antimony, ormixtures thereof. Examples of materials suitable for use assemiconductor nanocrystal cores include, but are not limited to, CdS,CdO, CdSe, CdTe, ZnS, ZnO, ZnSe, ZnTe, MgTe, GaAs, GaP, GaSb, GaN, HgS,HgO, HgSe, HgTe, InAs, InP, InSb, InN, AlAs, AlP, AlSb, AlS, PbS, PbO,PbSe, Ge, Si, alloys thereof, and/or mixtures thereof, including ternaryand quaternary alloys and/or mixtures. Other non-limiting examples areprovided above. Examples of materials suitable for use as semiconductornanocrystal shells include, but are not limited to, CdS, CdO, CdSe,CdTe, ZnS, ZnO, ZnSe, ZnTe, MgTe, GaAs, GaP, GaSb, GaN, HgS, HgO, HgSe,HgTe, InAs, InP, InSb, InN, AlAs, AlP, AlSb, AlS, PbS, PbO, PbSe, Ge,Si, alloys thereof, and/or mixtures thereof, including ternary andquaternary alloys and/or mixtures. Other non-limiting examples areprovided above.

In certain embodiments, the surrounding “shell” material can have abandgap greater than the bandgap of the core material. In certainembodiments, the shell can be chosen so as to have an atomic spacingclose to that of the “core” substrate. In certain embodiments, thesurrounding shell material can have a bandgap less than the bandgap ofthe core material. In a further embodiment, the shell and core materialscan have the same crystal structure. Examples of semiconductornanocrystals (core)shell structures include, without limitation:(CdSe)ZnS (core)shell, (CdZnSe)CdZnS (core)shell, and (CdS)CdZnS(core)shell.

For further examples of core/shell semiconductor structures, see U.S.application Ser. No. 10/638,546, entitled “Semiconductor NanocrystalHeterostructures”, filed 12 Aug. 2003, which is hereby incorporatedherein by reference in its entirety.

The semiconductor nanocrystals are preferably members of a population ofsemiconductor nanocrystals having a narrow size distribution. Morepreferably, the semiconductor nanocrystals comprise a monodisperse orsubstantially monodisperse population of semiconductor nanocrystals. Themonodisperse distribution of diameters can also be referred to as asize. In certain embodiments, the monodisperse population ofsemiconductor nanocrystals exhibits less than a 15% rms deviation indiameter of the nanocrystals, preferably less than 10%, more preferablyless than 5%.

Methods of preparing monodisperse semiconductor nanocrystals includepyrolysis of organometallic reagents, such as dimethyl cadmium, injectedinto a hot, coordinating solvent. This permits discrete nucleation andresults in the controlled growth of macroscopic quantities ofnanocrystals. Preparation and manipulation of semiconductor nanocrystalsare described, for example, in U.S. Pat. Nos. 6,322,901 and 6,576,291,and U.S. Patent Application No. 60/550,314, each of which is herebyincorporated herein by reference in its entirety. Additional examples ofmethods of preparing semiconductor nanocrystal are described in U.S.patent application Ser. No. 11/354,185 of Bawendi et al., entitled“Light Emitting Devices Including Semiconductor Nanocrystals”, filed 15Feb. 2006, and U.S. patent application Ser. No. 11/253,595 ofCoe-Sullivan et al., entitled “Light Emitting Device IncludingSemiconductor Nanocrystals”, filed 21 Oct. 2005, and U.S. patentapplication Ser. No. 10/638,546 of Kim et al., entitled “SemiconductorNanocrystal Heterostructures”, filed 12 Aug. 2003, referred to above,each of which is hereby incorporated by reference herein in itsentirety.

One method of manufacturing a nanocrystal comprises a colloidal growthprocess. Colloidal growth occurs by rapidly injecting an M donor and anX donor into a hot coordinating solvent. The injection produces anucleus that can be grown in a controlled manner to form a nanocrystal.The reaction mixture can be gently heated to grow and anneal thenanocrystal. Both the average size and the size distribution of thenanocrystals in a sample are dependent on the growth temperature. Thegrowth temperature necessary to maintain steady growth increases withincreasing average crystal size. The nanocrystal is a member of apopulation of nanocrystals. As a result of the discrete nucleation andcontrolled growth, the population of nanocrystals obtained has a narrow,monodisperse distribution of diameters. The monodisperse distribution ofdiameters can also be referred to as a size. The process of controlledgrowth and annealing of the nanocrystals in the coordinating solventthat follows nucleation can also result in uniform surfacederivatization and regular core structures. As the size distributionsharpens, the temperature can be raised to maintain steady growth. Byadding more M donor or X donor, the growth period can be shortened.

The M donor can be an inorganic compound, an organometallic compound, orelemental metal. M is cadmium, zinc, magnesium, mercury, aluminum,gallium, indium or thallium. The X donor is a compound capable ofreacting with the M donor to form a material with the general formulaMX. Typically, the X donor is a chalcogenide donor or a pnictide donor,such as a phosphine chalcogenide, a bis(silyl) chalcogenide, dioxygen,an ammonium salt, or a tris(silyl) pnictide. Suitable X donors includedioxygen, bis(trimethylsilyl) selenide ((TMS)₂Se), trialkyl phosphineselenides such as (tri-n-octylphosphine) selenide (TOPSe) or(tri-n-butylphosphine) selenide (TBPSe), trialkyl phosphine telluridessuch as (tri-n-octylphosphine) telluride (TOPTe) orhexapropylphosphorustriamide telluride (HPPTTe),bis(trimethylsilyl)telluride ((TMS)₂Te), bis(trimethylsilyl)sulfide((TMS)₂S), a trialkyl phosphine sulfide such as (tri-n-octylphosphine)sulfide (TOPS), an ammonium salt such as an ammonium halide (e.g.,NH₄Cl), tris(trimethylsilyl) phosphide ((TMS)₃P), tris(trimethylsilyl)arsenide ((TMS)₃As), or tris(trimethylsilyl) antimonide ((TMS)₃Sb). Incertain embodiments, the M donor and the X donor can be moieties withinthe same molecule.

A coordinating solvent can help control the growth of the nanocrystal.The coordinating solvent is a compound having a donor lone pair that,for example, has a lone electron pair available to coordinate to asurface of the growing nanocrystal. Solvent coordination can stabilizethe growing nanocrystal. Typical coordinating solvents include alkylphosphines, alkyl phosphine oxides, alkyl phosphonic acids, or alkylphosphinic acids, however, other coordinating solvents, such aspyridines, furans, and amines may also be suitable for the nanocrystalproduction. Examples of suitable coordinating solvents include pyridine,tri-n-octyl phosphine (TOP), tri-n-octyl phosphine oxide (TOPO) andtris-hydroxylpropylphosphine (tHPP). Technical grade TOPO can be used.In certain embodiments, a non-coordinating solvent can be used.

Size distribution during the growth stage of the reaction can beestimated by monitoring the absorption line widths of the particles.Modification of the reaction temperature in response to changes in theabsorption spectrum of the particles allows the maintenance of a sharpparticle size distribution during growth. Reactants can be added to thenucleation solution during crystal growth to grow larger crystals. Bystopping growth at a particular nanocrystal average diameter andchoosing the proper composition of the semiconducting material, theemission spectra of the nanocrystals can be tuned continuously over thewavelength range of 300 nm to 5 microns, or from 400 nm to 800 nm forCdSe and CdTe. The nanocrystal has a diameter of less than 150 Å. Apopulation of nanocrystals has average diameters in the range of 15 Å to125 Å.

A semiconductor nanocrystal can have various shapes, including, but notlimited to, sphere, rod, disk, other shapes, and mixtures of variousshaped particles.

As discussed above, in certain embodiments, semiconductor nanocrystalcan include a core/shell structure. In such embodiments, a semiconductornanocrystal can include a core of a semiconductor material. Asemiconductor nanocrystal core can comprise, for example, and withoutlimitation, a semiconductor material represented by the formula MX,where M is cadmium, zinc, magnesium, mercury, aluminum, gallium, indium,thallium, or mixtures thereof, and X is oxygen, sulfur, selenium,tellurium, nitrogen, phosphorus, arsenic, antimony, or mixtures thereof.Other examples are provided elsewhere herein.

In embodiments including a core/shell structure, the core includes ashell (also referred to as an overcoating) on a surface of the core. Theovercoating can be a semiconductor material having a compositiondifferent from the composition of the core. The overcoating of asemiconductor material on a surface of the nanocrystal core can include,for example, and without limitation, Group II-VI compounds, Group II-Vcompounds, Group III-VI compounds, Group III-V compounds, Group IV-VIcompounds, Group I-III-VI compounds, Group II-IV-VI compounds, and GroupII-IV-V compounds, for example, ZnO, ZnS, ZnSe, ZnTe, CdO, CdS, CdSe,CdTe, HgO, HgS, HgSe, HgTe, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb,GaSe, InN, InP, InAs, InSb, TlN, TlP, TlAs, TlSb, PbO, PbS, PbSe, PbTe,Si, Ge, alloys thereof and/or mixtures thereof. For example, ZnS, ZnSeor CdS overcoatings can be grown on CdSe or CdTe nanocrystals. Anovercoating process is described, for example, in U.S. Pat. No.6,322,901. By adjusting the temperature of the reaction mixture duringovercoating and monitoring the absorption spectrum of the core, overcoated materials having high emission quantum efficiencies and narrowsize distributions can be obtained. In certain embodiments, theovercoating can be between 1 and 10 monolayers thick.

The particle size distribution can be further refined by size selectiveprecipitation with a poor solvent for the nanocrystals, such asmethanol/butanol as described in U.S. Pat. No. 6,322,901. For example,nanocrystals can be dispersed in a solution of 10% butanol in hexane.Methanol can be added dropwise to this stirring solution untilopalescence persists. Separation of supernatant and flocculate bycentrifugation produces a precipitate enriched with the largestcrystallites in the sample. This procedure can be repeated until nofurther sharpening of the optical absorption spectrum is noted.Size-selective precipitation can be carried out in a variety ofsolvent/nonsolvent pairs, including pyridine/hexane andchloroform/methanol. The size-selected nanocrystal population can haveno more than a 15% rms deviation from mean diameter, preferably 10% rmsdeviation or less, and more preferably 5% rms deviation or less.

In certain embodiments, semiconductor nanocrystals are optionallysurface modified, including, but not limited to, for example, having oneor more ligand groups attached thereto.

In one embodiment, the ligands are derived from the coordinating solventused during the growth process. The surface can be modified by repeatedexposure to an excess of a competing coordinating group to form anoverlayer. For example, a dispersion of the capped semiconductornanocrystal can be treated with a coordinating organic compound, such aspyridine, to produce crystallites which disperse readily in pyridine,methanol, and aromatics but no longer disperse in aliphatic solvents.Such a surface exchange process can be carried out with any compoundcapable of coordinating to or bonding with the outer surface of thesemiconductor nanocrystal, including, for example, phosphines, thiols,amines and phosphates. The semiconductor nanocrystal can be exposed toshort chain polymers which exhibit an affinity for the surface and whichterminate in a moiety having an affinity for a suspension or dispersionmedium. Such affinity improves the stability of the suspension anddiscourages flocculation of the semiconductor nanocrystal. Nanocrystalouter layers are described in U.S. Pat. No. 6,251,303, which isincorporated by reference in its entirety.

More specifically, the coordinating ligand can have the formula:

wherein k is 2, 3 or 5, and n is 1, 2, 3, 4 or 5 such that k−n is notless than zero; X is O, S, S═O, SO₂, Se, Se═O, N, N═O, P, P═O, As, orAs═O; each of Y and L, independently, is aryl, heteroaryl, or a straightor branched C₂₋₁₂ hydrocarbon chain optionally containing at least onedouble bond, at least one triple bond, or at least one double bond andone triple bond. The hydrocarbon chain can be optionally substitutedwith one or more C₁₋₄ alkyl, C₂₋₄ alkenyl, C₂₋₄ alkynyl, C₁₋₄ alkoxy,hydroxyl, halo, amino, nitro, cyano, C₃₋₅ cycloalkyl, 3-5 memberedheterocycloalkyl, aryl, heteroaryl, C₁₋₄ alkylcarbonyloxy, C₁₋₄alkyloxycarbonyl, C₁₋₄ alkylcarbonyl, or formyl. The hydrocarbon chaincan also be optionally interrupted by —O—, —S—, —N(R^(a))—,—N(R^(a))—C(O)—O—, —O—C(O)—N(R^(a))—, —N(R^(a))—C(O)—N(R^(b))—,—O—C(O)—O—, —P(R^(a))—, or —P(O)(R^(a))—. Each of R^(a) and R^(b),independently, is hydrogen, alkyl, alkenyl, alkynyl, alkoxy,hydroxylalkyl, hydroxyl, or haloalkyl. An aryl group is a substituted orunsubstituted cyclic aromatic group. Examples include phenyl, benzyl,naphthyl, tolyl, anthracyl, nitrophenyl, or halophenyl. A heteroarylgroup is an aryl group with one or more heteroatoms in the ring, forinstance furyl, pyiridyl, pyrrolyl, phenanthryl.

A suitable coordinating ligand can be purchased commercially or preparedby ordinary synthetic organic techniques, for example, as described inJ. March, Advanced Organic Chemistry, which is incorporated herein byreference in its entirety. See also U.S. patent application Ser. No.10/641,292 entitled “Stabilized Semiconductor Nanocrystals”, filed 15Aug. 2003, which is hereby incorporated herein by reference in itsentirety. See also other patents and patent applications referencedherein for additional descriptions of preparation methods.

Transmission electron microscopy (TEM) can provide information about thesize, shape, and distribution of the nanocrystal population. PowderX-ray diffraction (XRD) patterns can provide the most completeinformation regarding the type and quality of the crystal structure ofthe nanocrystals. Estimates of size are also possible since particlediameter is inversely related, via the X-ray coherence length, to thepeak width. For example, the diameter of the nanocrystal can be measureddirectly by transmission electron microscopy or estimated from X-raydiffraction data using, for example, the Scherrer equation. It also canbe estimated from the UV/Vis absorption spectrum.

As discussed above, certain embodiments of a composition can includenanomaterial and a carrier medium (e.g., liquid, polymer, monomer,polymer or monomer solution, etc.). In certain embodiments, a carriermedium can be one in which the nanomaterial does not dissolve or doesnot appreciably dissolve (e.g., solubility is less than 0.001 mg/ml). Incertain embodiments including a nanomaterial with one or more attachedligands, the carrier medium can be one in which the ligand not solubleor not appreciably soluble. In other embodiments, the medium can be onein which the ligand is at least partially soluble.

Examples of a liquid component for inclusion in compositions includingnanomaterial (e.g, without limitation, semiconductor nanocrystals)includes, without limitation, those listed in the following Table 1, andmixtures of two or more thereof. Examples of mixtures include hexane andoctane; benzene and xylene; tetrahydrofurane and anisole; etc.

TABLE 1 Boiling Relative Polarity Viscosity Point (compared to LiquidFormula @25° C. @1 atm water) cyclohexane C₆H₁₂ 0.89 80.7 0.006 pentaneC₅H₁₂ 0.24 36.1 0.009 hexane C₆H₁₄ 0.30 69 0.009 heptane C₇H₁₆ 0.91 980.012 carbon tetrachloride CCl₄ 0.91 76.7 0.052 p-xylene C₈H₁₀ 0.63138.3 0.074 toluene C₇H₈ 0.56 110.6 0.099 benzene C₆H₆ 0.60 80.1 0.111diethyl ether C₄H₁₀O 0.22 34.6 0.117 methyl t-butyl alcohol C₅H₁₂O 55.20.148 dioxane C₄H₈O₂ 1.21 101.1 0.164 tetrahydrofurane (THF) C₄H₈O 0.4766 0.207 ethyl acetate C₄H₈O₂ 77 0.228 dimethoxy-ethane (glyme) C₄H₁₀O₂85 0.231 diglyme C₆H₁₄O₃ 162 0.244 chloroform CHCl₃ 0.54 61.2 0.259methylene chloride CH₂Cl₂ 0.43 39.8 0.309 2-butanone C₄H₈O 79.6 0.327acetone C₃H₆O 0.31 56.2 0.355 t-butyl alcohol C₄H₁₀O 82.2 0.389dimethyl-formamide C₃H₇NO 153 0.404 (DMF) dimethyl sulfoxide C₂H₆OS 1890.444 (DMSO) acetonitrile C₂H₃N 0.35 81.6 0.46 2-propanol C₃H₈O 2.4082.4 0.546 1-butanol C₄H₁₀O 3.00 117.6 0.602 1-propanol C₃H₈O 1.95 970.617 acetic acid C₂H₄O₂ 118 0.648 ethanol C₂H₆O 1.20 78.5 0.654diethylene glycol C₄H₁₀O₃ 35.70 245 0.713 methanol CH₄O 0.59 64.6 0.762ethylene glycol C₂H₆O₂ 16.90 197 0.79 glycerin C₃H₈O₃ 1410.00 290 0.812water, heavy (D2O) D₂O 101.3 0.991 water H₂O 1.00 100 1 Nonane(CH₃(CH₂)₇CH₃) 0.67 39.0 Decane C₁₀H₂₂ 0.84 174.1 Dodecane C₁₂H₂₆ 1.25216.2 Chlorobenzene C₆H₅Cl 0.75 132 Dichlorobenzene C₆H₄Cl₂ — 174.0Anisole C₇H₈O 0.92 154.0 Dimethyl formamide HCON(CH₃)₂ 0.79 149.561-Methyl-2-pyrrolidinone 1.7 204.5 Carbon tetrachloride CCl₄ 0.91 76.81,1,1-Trichloroethane CH₃CCl₃ 0.73 74.0 Tetrachloroethylene ClCH═CCl₂0.57 87.0 Ethylbenzene C₈H₁₀ 0.67 136.0

Other liquids or mixtures of liquids can be used. In certainembodiments, volatile liquids or mixtures of volatile liquids can beused.

In certain embodiments, a composition including nanomaterial and aliquid has a viscosity in a range of from about 0.1 centipoise (e.g.,that of diethyl ether, methanol) to greater than 1500 centipoise (e.g.,that of oils, glycerol). A composition including a nanomaterial andliquid may also be referred to as an ink.

In embodiments including nanomaterial comprising semiconductornanocrystals, a preferred liquid comprises an organic non-polar solvent.More preferably, such carrier has a viscosity less than or equal toabout 1 cP and also relatively high volatility.

Optionally, other components can be included in the composition.Examples of other components that can be optionally included in thecomposition include, but are not limited to, e.g., surfactants,solvents, co-solvents, buffers, biocides, viscosity modifiers,complexing agents, chelating agents, stabilizing agents (e.g., toinhibit agglomeration of the nanomaterial), humectants etc. Otherpossible components include other additives of the type that may beincluded in ink or inkjet ink compositions. Stabilizing agents caninclude, e.g., chemically attached functional groups or ligands to forma coating around individual nanoparticles.

The amount (e.g., concentration (wt/vol)) of nanomaterial included in acomposition can be selected based upon the particular nanomaterial anddesired attributes of the deposited nanomaterial (e.g., thickness,optical density, features of the deposited nanomaterial (e.g., patternedor unpatterned, sizes of the features of a pattern, etc.)). The amountcan be readily determined by a person of ordinary skill in the art.

For example, in certain embodiments of compositions includingsemiconductor nanocrystals and a carrier medium (including, e.g., butnot limited to, a liquid comprising non-polar organic solvent or solventmixture), the composition includes at least about 0.1 mg/mlsemiconductor nanocrystals and/or composition. In examples of otherembodiments, the composition can include at least 1 mg/ml, at least 5mg/ml, at least 10 mg/ml, at least 25 mg/ml; at least 50 mg/ml, etc.

In certain preferred embodiments, the nanomaterial and any otheroptional solid components are dispersed in the composition whenintroduced onto the transfer surface. In certain preferred embodiments,the dispersion is colloidal.

In accordance with one aspect of the invention, there is provided acomposition useful for depositing nanomaterial onto a substrate. Thecomposition includes nanomaterial. The composition can further include acarrier medium (e.g., without limitation, liquid, polymer, monomer,polymer or monomer solution, etc.). Optionally, the composition canfurther include one or more additional components. In certainembodiments, nanomaterial comprises nanoparticles.

Methods in accordance with the invention allow deposition of one or morenanomaterials and/or one or more compositions including nanomaterialonto a substrate. Such nanomaterial(s) and/or composition(s) can bedeposited onto the substrate in a patterned or unpatterned arrangement.

Methods in accordance with the invention are particularly useful forapplying one or more nanomaterials to a predefined region of asubstrate, which may optionally include other materials, layers,components, and/or structures disposed thereon. As discussed above,nanomaterial can also be deposited with additional components includedin a composition.

The predefined region is a region on the substrate where thenanomaterial can be selectively applied. The nanomaterial and surfacecan be chosen such that the nanomaterial remains substantially entirelywithin the predetermined area. Nanomaterial can be deposited onto thesubstrate such that the nanomaterial forms an unpatterned layercomprising nanomaterial within the predetermined area or a patterncomprising nanomaterial within the predetermined area. The pattern canbe a regular pattern (such as an array, or a series of lines), or anirregular pattern.

Once one or more nanomaterials are deposited onto the substrate, thesubstrate can have a region including the nanomaterial (the predefinedregion) and a region substantially free of nanomaterial. In somecircumstances, the one or more nanomaterials are deposited onto thesubstrate at a thickness of about a monolayer. In some circumstances,the thickness can be greater than a monolayer. The predefined region canbe a discontinuous region. In other words, when the one or morenanomaterials are deposited onto the predefined region of the substrate,locations including nanomaterial can be separated by other locationsthat are substantially free of nanomaterial.

See, for example, A. Kumar and G. Whitesides, Applied Physics Letters,63, 2002-2004, (1993); and V. Santhanam and R. P. Andres, Nano Letters,4, 41-44, (2004), each of which is incorporated by reference in itsentirety. See also U.S. patent application Ser. No. 11/253,612, filed 21Oct. 2005, entitled “Method And System For Transferring A PatternedMaterial”, of Coe-Sullivan et al. and U.S. patent application Ser. No.11/253,595, filed 21 Oct. 2005, entitled “Light Emitting DeviceIncluding Semiconductor Nanocrystals,” of Coe-Sullivan, each of which isincorporated herein by reference in its entirety.

When deposited in a patterned arrangement, nanomaterial can be depositedin a pattern comprising features having at least one dimension at amicron-scale (e.g., less than 1 mm, less than 500 μm, less than 200 μm,less than 100 μm or less, less than 50 μm or less, less than 20 μm orless, or less than 10 μm or less). Nanomaterial can also be deposited ina patterned arrangement comprising features at greater thanmicron-scale.

A pattern comprising deposited nanomaterial having features on themicron scale may also be referred to herein as a micropattern.

For example, a micropattern including 10-20 μm size features can beuseful in light emitting device applications including, e.g.,semiconductor nanocrystals.

The surface on which the nanomaterial can be deposited can havedimensions of 1 cm or greater, 10 cm or greater, 100 cm or greater, or1,000 cm or greater.

Methods in accordance with the invention are scalable and can be usefulin depositing a pattern comprising one or more nanomaterials over a widerange of surface areas.

For example, the method is useful for depositing nanomaterial over verysmall areas (for example, 100 μm catheters) to very large areas, (forexample, 12″ square areas). In further example, the method is alsouseful for depositing nanomaterial over surfaces with dimensions such asGEN2 (360 mm×465 mm), GEN3 (550 mm×650 mm), GEN3.5 (600 mm×720 mm), GEN4(730 mm×920 mm), GEN5 (1110 mm×1250 mm), GEN6 (1500 mm×1800 mm), GEN7(1900 mm×2100 mm), and subsequent generations of glass that can be used,e.g., in displays. Optionally, areas onto which nanomaterial is appliedcan then be stitched (or tiled) together, to expand the printable areafrom 12″ squares, to ‘n×12″ squares’ as is frequently done in thesemiconductor lithography field.

In accordance with one aspect of the invention, a method of depositingnanomaterial onto a substrate includes applying a composition comprisingnanomaterial to an applicator surface from a transfer surface; andcontacting the applicator surface to a substrate to deposit the one ormore nanomaterials thereto.

As discussed above, in addition to nanomaterial, a composition canfurther include liquid or another carrier medium. Optionally, acomposition can further include other components.

In accordance with another aspect of the invention, there is provided amethod for depositing nanomaterial onto a substrate. The method includesapplying nanomaterial to an applicator surface from a transfer surface,and contacting the applicator surface to the substrate. The nanomaterialincluded on the applicator can be patterned or unpatterned. A patterncan comprise an array of individual features at least one of whichcomprises nanomaterial. Typically, the individual features are spacedapart from each other. In certain embodiments, however, the featurescould be in contact with each other or even overlap.

In accordance with a further aspect of the invention, there is provideda method for depositing nanomaterial onto a substrate. The methodincludes applying a layer comprising nanomaterial to an applicatorsurface from a transfer surface, and contacting the applicator surfaceto the substrate to deposit at least a portion of nanomaterial thereto.The layer including nanomaterial applied to the applicator can bepatterned or unpatterned

As discussed above, nanomaterial deposited by a method in accordancewith the invention can include one or more nanomaterials, including,e.g., a mixture of two or more different nanomaterials. Whennanomaterial is included in a composition, and two or more nanomaterialsare to be deposited, different compositions including one or moredifferent nanomaterials can be used.

If two or more different nanomaterials or mixtures of nanomaterials areto be deposited onto a substrate, for example, the method can includeapplying different nanomaterials and/or mixtures of nanomaterials to anapplicator surface from a transfer surface in a single application stepand a single deposition step. In another embodiment, the method caninclude applying different compositions including differentnanomaterials and/or mixtures of nanomaterials to an applicator surfacefrom a transfer surface in a single application step and a singledeposition step.

In another example, the method can include applying differentnanomaterials and/or mixtures of nanomaterials to an applicator surfacefrom separate transfer surfaces in more than one application step and asingle deposition step. In another example, the method can includeapplying different compositions including different nanomaterials and/ormixtures of nanomaterials to an applicator surface from separatetransfer surfaces in more than one application step and a singledeposition step.

In an additional example, the method can include applying differentnanomaterials and/or mixtures of nanomaterials to separate applicators(e.g., from separate transfer surfaces, from a transfer surface that isclean and refilled between applications of nanomaterials to separateapplicators, etc.) and separate deposition steps. In another example,the method can include applying different compositions includingdifferent nanomaterials and/or mixtures of nanomaterials to separateapplicators (e.g., from separate transfer surfaces, from a transfersurface that is clean and refilled between applications of compositionsto the separate applicators, etc.) and separate deposition steps. Othervariations, including, for example, inclusion of optional additionalsteps are also contemplated.

If a composition includes liquid, in certain embodiments, all orsubstantially all of the liquid can be removed from the compositionafter the composition is applied to the applicator surface. This allowsthe nanomaterial and any optional non-liquid components of a compositionto be deposited onto the substrate by a dry (e.g., liquid-free orsubstantially liquid-free) transfer. A method including a dry transferof nanomaterials onto the substrate can be advantageous when a liquidincluded in a composition can dissolve or otherwise react with thesubstrate.

A dry transfer process is preferred, for example, when transferring acomposition including semiconductor nanocrystals from an applicator toan organic layer of a light-emitting device structure during devicefabrication.

If interaction between the substrate and a liquid component is not aconcern, the composition can be deposited onto the substrate withoutprior removal the liquid therefrom. The liquid can be removed afterdeposition of the composition(s) onto the substrate.

If a wet transfer is desired, and the liquid is appreciably volatile atambient conditions, the time between application of composition(s) tothe applicator surface and deposition thereof onto the substrate iscontrolled to allow the deposition to occur while the composition(s)includes at least an amount of liquid.

In certain embodiments of the invention, a method of depositing one ormore nanomaterials onto a substrate includes applying one or moreliquid-free or substantially liquid-free nanomaterials to an applicatorfrom a transfer surface; and depositing at least a portion of thenanomaterials from the applicator onto the substrate.

This aspect of the invention can be particularly advantageous whendepositing one or more nanomaterials onto a substrate in a predeterminedpattern. By including a transfer of nanomaterial(s) from the transfersurface to the applicator in the absence of a liquid component, blurringor distortion of patterned nanomaterial on the applicator surface can bereduced. Such blurring or distortion can occur, for example, when theliquid including nanomaterial spreads on or wets the applicator surface.

A transfer surface can be planar or contoured. A transfer surface can berigid or flexible.

A transfer surface can be featureless or smooth (e.g. without elevationsand/or depressions (e.g., grooves, recessed wells, etc.). A smoothtransfer surface can be useful, for example, in a method for depositingan unpatterned layer onto a substrate. Examples of other embodimentsincluding a smooth transfer surface are described below.

A transfer surface can include one or more features (e.g., elevationsand/or depressions (e.g., grooves, recessed wells, otherthree-dimensional features, etc.)). The arrangement of features cancorrespond to a predetermined pattern to be deposited onto a substrate.For example, in certain embodiments, a transfer surface including one ormore depressions (e.g., grooves, recessed wells, other three dimensionalfeatures, etc.) can be useful, for example, in a method for depositing apattern comprising one or more nanomaterials onto a substrate. Atransfer surface including elevated features can also be useful fordepositing a pattern onto a substrate. For example, a compositionincluding nanomaterial disposed on the elevated features of the transfersurface can be picked up with an applicator in the predetermined patternand deposited onto the substrate.

A transfer surface can include a planar surface. A transfer surface caninclude a non-planar surface.

Examples of transfer surfaces include, without limitation, a plateincluding a flat section of material (metallic, polymeric, silicon, forexample), that can be smooth or include one or more depressions (e.g., aflat cliché), a roller (e.g., with a circular, elliptical, or otherrounded cross-section) including a predetermined pattern, a rollershaped transfer surface with a smooth surface (e.g., a roller shapedcliché), etc.

One type of transfer surface useful in the present invention is known inthe art as a cliché. Other types of transfer surfaces can also bereadily identified and used.

In certain embodiments, a rigid transfer surface is preferred.

In certain embodiments, the transfer surface is made of polymer linedsteel, thin (˜1 mm) steel sheet or thick (˜10 mm) steel plate. Othermaterials that can be used to fabricate a transfer surface include metal(e.g., aluminum, etc.) metal alloys, silicon, glass, ceramic, etc.Preferably, the transfer surface is fabricated from steel plate.

In embodiments of transfer surfaces including one or more grooves, theshape of the grooves can be rectangular or another geometric shape suchas lines, square, triangular, circular, semi-circular, elliptical,semi-elliptical, other geometrical shapes, irregular shapes, customizedshapes, etc. The grooves can have the same shape or may include anynumber of different combinations of geometrical, irregular, customized,etc. shapes, for example.

The dimensions of a groove, for example, can optionally be on a micronscale (e.g., less than 1 mm, less than 500 μm, less than 200 μm, lessthan 100 μm, less than 50 μm, or 20 μm, 10 μm or less), or on amillimeter-scale or on a centimeter-scale or larger. Larger or smallerdimension grooves can also be used, depending on the predeterminedpattern to be applied to substrate.

For example, the depth of a groove may be 0.01 μm (10 nm) to 100 μm, butis typically 25 μm in depth.

In embodiments of a transfer surface including two or more grooves, thegrooves can be arranged in a pattern.

In embodiments of a transfer surface including depressions (e.g.,grooves, recessed wells, other three dimension features, etc.) arrangedin a pattern, the size, shape, and arrangement of the patterneddepressions in a transfer surface can be designed so as to correspond toa predetermined pattern to be deposited onto the substrate. The depthand contour of the depressions in the transfer surface are also designedto produce the predetermined pattern to be deposited onto the substrate.

For example, use of a transfer surface including a predetermined patternof elevations or depressions (e.g., grooves, recessed wells, other threedimensional features, etc.) will permit the transfer of a predeterminedpattern from the transfer surface to the applicator surface. A patterncan be formed on a transfer surface by, for example, etching, generalphotolithography, or other known techniques in the relevant art.

FIG. 1A illustrates a plan view of an example of a cliché 100. As shown,a pattern of rectangular shaped grooves 102 is formed in the surface 104of the cliché. Although the figure depicts rectangular shaped grooves,as discussed above, the shape, size, arrangement, depth, and contour ofthe grooves are selected based on the predetermined pattern to bedeposited onto the substrate.

FIG. 1 B illustrates a plan view of another example of a cliché 100. Asshown, the pattern of line-shaped grooves 102 is formed in the surface104 of the cliché. The cliché includes a pattern of lines with differentwidths and different spacings. The figure contemplates that the clichégrooves will be filled with three different colored compositions (e.g.,red, green, and blue). Optionally, fewer or more different compositionscan be included in the grooves.

When a transfer surface includes a pattern of grooves, nanomaterial,and/or a composition including nanomaterial, can be introduced into oneor more grooves in accordance with depositing the predetermined patternincluding nanomaterial onto a substrate. The one or more nanomaterialsor compositions can be included in at least a portion of a groove inaccordance with the individual features of the predetermined pattern tobe deposited on a substrate. As discussed above, the nanomaterial and/orcomposition included in the various grooves can be the same ordifferent.

When an applicator is contacted (e.g., by pressing) to the transfersurface and thereafter separated therefrom, the predetermined patternincluding the composition(s) and/or nanomaterial(s) included in thegrooves of the transfer surface, as the case may be, preferably becomesreversibly adhered to the applicator. The predetermined patterned isthereafter deposited onto the substrate by contacting the applicatorthereto.

As discussed above, in certain embodiments, a predetermined pattern canbe deposited onto the substrate by including elevated features,corresponding to the predetermined pattern, on all or a portion of thetransfer surface. In which embodiments, the nanomaterial disposed on theelevated features of the transfer surface can be picked up with anapplicator in the predetermined pattern and deposited onto the substrateby contacting the applicator thereto.

In the various aspects of the invention, nanomaterial disposed on thetransfer surface can be selectively removed in a predetermined patternto be deposited onto the substrate.

For example, in certain embodiments, the transfer surface can be smoothor unpatterned. In such embodiments, one or more nanomaterials and/orone or more compositions comprising nanomaterial can be applied to thesmooth transfer surface and a featured applicator can be used to pick-upand deposit a pattern including the composition(s) or nanomaterial(s),in the arrangement of the applicator features onto the substrate.Alternatively, one or more nanomaterials and/or one or more compositionscomprising nanomaterial can be applied to the smooth transfer surfaceand a smooth or featureless applicator can be used to pick-up anddeposit an unpatterned layer including the composition(s) ornanomaterial(s) onto the substrate.

In certain embodiments, for example, the nanomaterial can be removedfrom the transfer surface in a predetermined pattern by a patternedapplicator (e.g., stamp, roller, etc.) with features (elevations and/ordepressions) on the applicator surface corresponding to thepredetermined pattern. In certain embodiments, a first patterncomprising nanomaterial can be removed by a first applicator and thesubtractive pattern comprising nanomaterial disposed on the transfersurface can be picked up by a second applicator and deposited onto thesubstrate.

In another aspect, a featureless applicator can deposit an unpatternedlayer comprising one or more nanomaterials from a smooth transfersurface.

In certain other embodiments including an unpatterned transfer surface,a featureless applicator can be used to deposit a pattern comprising oneor more compositions or nanomaterials formed on the unpatterned transfersurface by, e.g., inkjet printing, silk-screening, other screen-printingtechnique, or other known technique for creating a pattern comprisingone or more compositions or nanomaterials on the smooth transfersurface. A pattern formed on a transfer surface in such mannercorresponds to the predetermined pattern including one or morenanomaterials to be deposited onto the substrate.

In another aspect of the invention, for example, a predetermined patterncan be formed on a transfer surface with use of a mask including one ormore apertures. The number, size, shape, and arrangement of theapertures will be selected based on the predetermined pattern that isdesired.

In certain embodiments, an example of which is depicted in FIG. 2 A, forexample, a mask including one or more apertures corresponding to thepredetermined pattern can be placed on the transfer surface before thenanomaterial and/or composition is to be picked up by the applicator. Insuch case, the applicator surface, preferably unfeatured, can pick upthe nanomaterial and/or composition including nanomaterial from thetransfer surface through the apertures arranged in a predeterminedpattern to form patterned nanomaterial and/or composition thereon. Theapplicator including the patterned nanomaterial and/or composition canthereafter be contacted to the substrate to deposit the pattern thereon.The nanomaterial and/or composition is preferably introduced to thetransfer surface prior to positioning the mask thereon. In certainembodiments, any liquid is preferably removed from the nanomaterialand/or composition prior to positioning of the mask on the transfersurface.

In certain other embodiments (not shown), nanomaterial and/or acomposition including nanomaterial is deposited onto the transfersurface through a mask including one or more apertures arranged in thepredetermined pattern. After the mask is removed, the patternednanomaterial deposited onto transfer surface through the apertures canbe picked up by an applicator, preferably with an unfeatured surface.The nanomaterial can thereafter be deposited onto the substrate from theapplicator surface.

In certain preferred embodiments, an example of which is depicted inFIG. 2 B, a predetermined pattern can be formed on a substrate bypositioning a mask including one or more apertures arranged in a desiredpredetermined pattern on the substrate prior to contacting theapplicator to the substrate. By contacting the applicator including thenanomaterial and/or composition to be applied to the substrate throughthe mask apertures, a pattern of the nanomaterial and/or composition isapplied to the substrate. In certain embodiments, the nanomaterialand/or composition on the applicator is preferably dry (e.g., at leastsubstantially free of liquid) prior contacting the applicator to thesubstrate through the mask apertures. In certain embodiments,nanomaterial may be deposited through less than all of the apertures. Incertain embodiments, the nanomaterial and/or composition on theapplicator preferably comprises an unpatterned layer. In certainembodiments involving printing of nanomaterial (preferably semiconductornanocrystals) and/or compositions including nanomaterials (preferablysemiconductor nanocrystals) in hybrid inorganic-organic devices, thedeposition (also referred to herein as printing) step(s) are preferablycarried out in a nitrogen or vacuum environment.

In an example of a preferred embodiment of the method partiallydescribed in FIG. 2B, a nanomaterial and/or composition includingnanomaterial is applied to an applicator. Preferably the applicator isdried to remove substantially all, and more preferably all, of anyliquid included in the nanomaterial and/or composition thereon. A maskincluding a predetermined pattern of apertures of a desired size andshape is inserted between the substrate and the applicator and alignedto the substrate. The applicator including the dried nanomaterial and/orcomposition is brought into contact with the substrate through theapertures at a predetermined pressure following which the applicator isreleased from the substrate (e.g., by releasing the pressure,translating the substrate, etc.). In embodiments including deposition ofone or more additional nanomaterials and/or compositions to the samesubstrate, the substrate can optionally be translated to a next locationfor a subsequent deposition step or alternatively, for example, thefirst mask can be cleaned and repositioned over the substrate for re-useor a different mask can be positioned over and aligned to the substrateand the next nanomaterial and/or composition deposited.

The foregoing process is particularly useful for depositingsemiconductor nanocrystal emissive materials in a process for makingvarious electro-optical devices including but not limited toelectroluminescent light-emitting devices and displays.

In certain embodiments, a mask can be fabricated from a class of filmscomprising polyimides including fluorinated polyimide films or filmcoated, at least on one side, with a fluorinated material. In certainembodiment, a film coated, on at least one side, with a coatingcomprising an aromatic material. In certain embodiments, one side of thefilm can be coated with a fluorinated material and the other side can becoated with an aromatic material.

In certain embodiments in which a side of the mask is positioned on thesubstrate, it is preferred to use a fluorinated polyimide film or filmcoated, at least on one side, with a fluorinated material, with the sideof the film including the fluorinated material being positioned againstthe substrate.

In certain embodiment, if a mask comprises plastic and/or a plasticcoating, it is preferably baked out at elevated temperature with vacuumto remove VOCs, etc. prior to printing.

Masks of different thickness can be used. By way of non-limitingexample, a mask comprising a polyimide film having a thickness of 1 milpolyimide can be used. Thinner and/or thicker masks are also suitable.Masks thinner than 0.5 mil are desirable for printing higher resolutionpatterns. Masks with a thickness less than 0.5 mil may requiretensioning. Alternatively, the rigidity and/or dimensional stability ofmasks with a thickness less than 0.5 mil can be enforce with a thinsteel foil. In certain other embodiments, a mask can comprise a rigidfoil which optionally can be coated on one or both sides with a softcoating (e.g, Teflon).

A mask can be patterned with a predetermined pattern by known techniques(including, but not limited to, photo-etching and laser patterning) orunpatterned.

Examples of film materials from which a mask can be made include,without limitation, polyimide films such as, for example, and withoutlimitation, 6FDA-ODA Fluorinated Polyimide, 6FDA-PMDA FluorinatedCo-Polyimide, 6FXDA-6FDA Fluorinated Polyimide Foam, Amoco Ultradel 4212HFDA-APBP Polyimide, Au/Cr/Polyimide Composite, BPDA-ODA Polyimide,BPDA-PDA Polyimide Film, BPDA-PFMB Polyimide, BTDA-APB Polyimide,BTDA-ODA Polyimide, BTDA-PDA Polyimide, Ciba-Geigy Probimide 348PMDA-ODA Polyimide, Ciba-Geigy Probimide 412 PSPI, Ciba-Geigy Probimide414 PSPI, Ciba-Geigy XU-287 Soluble Polyimide, Cu/Cr/BPDA-PDA PolyimideComposite, Cu/Cr/PMDA-ODA Polyimide Composite, DuPont 5810D BPDA-PDAPolyimide, DuPont 5879HP PMDA-ODA Polyimide, DuPont FPI-136M FluorinatedPolyimide, DuPont FPI-45M Fluorinated Polyimide, DuPont Kapton 100 HNPolyimide Film, DuPont Kapton 300H Polyimide Film, DuPont Kapton 500HNPolyimide Film, DuPont Kapton Type H Polyimide Film, DuPont Kapton TypeHN Polyimide Film, DuPont PI-2540 PMDA-4,4′-ODA Polyimide, DuPontPI-2545 PMDA-ODA Polyimide, DuPont PI-2556 BTDA-ODA-MPD Polyimide,DuPont PI-2560 BTDA-MPD-ODA Polyimide, DuPont PI-5878 PMDA-ODAPolyimide, DuPont Pyralin PI-2611 BPDA-PDA Polyimide, DuPont PyraluxPolyimide, GE Ultem Polyetherimide, Hitachi PIQ L100 Polyimide, HitachiPIX L 110 Polyimide, Mitsui Toatsu Aurum 450C Thermoplastic Polyimide,OMM Probimide 112A, OMM Probimide 114A, OMM Probimide 115A, OMMProbimide 116A, OMM Probimide 7005, OMM Probimide 7010, OMM Probimide7020, OMM Probimide 7505 PSPI, OMM Probimide 7510 PSPI, OMM Probimide7520 PSPI, PMDA-3,4′-ODA Polyimide, PMDA-3FDA Fluorinated Polyimide,PMDA-3FDA Fluorinated Polyimide Foam, PMDA-ODA Polyimide, PMDA-ODAm-diethylester, PMDA-PDA Polyimide Film, Probimide 32 Polyamide-imide,SE45 Siloxane-Polyimide, Upilex R Polyimide Film, and Upilex S PolyimideFilm.

A non-limiting example of a preferred mask comprises 001″±0.00015″ THICKKAPTON HN includes slots with predetermined dimensions. For example, oneembodiment of predetermined dimensions that can be used for printing aRed-Blue-Green subpixel arrangement for a display, can include lineapertures or slots are 400 or 450 microns wide on a 1500 micron pitch.

Optionally, a mask can further include a hole in each of the fourcorners to mount and tension a mask to a rigid frame, which is preferredwith thin masks, as discussed above. Various known techniques can beused to align a series of masks to be used to print and registermultiple nanomaterials on a single substrate.

In certain embodiments, the mask can be placed against the transfersurface or substrate without gaps in between the transfer surface orsubstrate, as the case may be, and the underside of the mask.

One or more nanomaterials or compositions can be transferred from thetransfer surface to an applicator by, for example, contacting (e.g.,pressing) the applicator against the transfer surface including the oneor more compositions or nanomaterials to be deposited.

The one or more compositions or nanomaterials transferred to theapplicator surface from the transfer surface preferably becomereversibly adhered to the applicator surface for later deposition ontothe substrate.

As discussed above, in certain embodiments, the one or more compositionscan thereafter be deposited from the applicator onto the substrate. If awet transfer of composition(s) onto the substrate is desired, the timebetween patterning the applicator and depositing the pattern onto thesubstrate is minimized to allow the pattern to transfer while thepatterned nanomaterial still includes at least an amount of the liquid.

As also discussed above, in certain other embodiments, the liquid can beremoved from composition(s) by, for example, evaporation, before theremainder of the composition (e.g., nanomaterial and any other optionalcomponents) is deposited on the substrate.

Certain other embodiments include a dual dry transfer. A dual drytransfer includes a liquid-free or substantially liquid-free transfer ofone or more nanomaterials from the transfer surface to the applicatorand a liquid-free or substantially liquid-free transfer or the one ormore nanomaterials from the applicator onto the substrate. Asubstantially liquid-free transfer includes, for example, no more thanabout 10 parts per hundred liquid, preferably no more than about 10parts per thousand liquid, and more preferably no more than about 10parts per million liquid.

For example, when one or more nanomaterials are introduced to a transfersurface as a component of a composition that also includes liquid, oneor more nanomaterials can be transferred from the transfer surface to anapplicator by, for example, contacting the applicator against thetransfer surface after the liquid is removed from the composition. Theliquid can be removed, for example, by evaporation at ambientconditions, by application or heat to accelerate evaporation, byadjusting the pressure to accelerate evaporation, by modifying thetemperature and pressure to accelerate evaporation, etc.

The one or more nanomaterials transferred to the applicator surface fromthe transfer surface preferably become reversibly adhered to theapplicator upon contacting the applicator to the transfer surface. Theone or more nanomaterials can thereafter be deposited from theapplicator onto the substrate.

As discussed above, a dry transfer process of one or more materials fromthe applicator onto the substrate can be advantageous when the liquid ofthe composition(s) including the nanomaterial(s) can dissolve orotherwise react with the surface of the substrate. Employing a drytransfer of nanomaterial(s) from the applicator onto the substrate freesthe substrate of solubility and surface chemistry requirements.

A dual dry transfer can also be used to deposit unpatterned layerscomprising nanomaterial.

Methods in accordance with the invention can be used to deposit apattern comprising two or more different nanomaterials onto a substrate.The two or more different nanomaterials can be deposited sequentially orin a single step.

For example, each of the two or more different compositions ornanomaterials can be deposited in sequential separate depositions steps.This embodiment can be used, for example, when depositing a patterncomprising different color compositions or nanomaterials, and each coloris deposited onto the substrate separately.

Preferably, each transfer is aligned and registered so that thepredetermined pattern is deposited onto the substrate at a predefinedlocation.

The method is compatible with various well-known alignment andregistration techniques for example, when more than one pattern isdeposited onto the substrate in more than one transfer. Factors that canaffect the registration of subsequent printing steps onto a singlesubstrate include multiple well pattern (e.g., groove) offset, as wellas the travel distance from one nanomaterial deposition to the next.Since both of these parameters can be tuned on the micron scale, highrepeatability after tuning is expected.

In certain embodiments, two or more different compositions ornanomaterials are deposited by a single transfer step. This can beachieved with use of a transfer surface which includes the two or moredifferent compositions or nanomaterials on the surface thereof. Forexample, the two or more nanomaterials can be included in the grooves ofa single transfer surface for simultaneous transfer. Alternatively, thetwo or more nanomaterials can by patterned on an smooth transfer surfaceby, e.g., inkjet or silk-screen printing, other screen-printingtechnique, vapor deposition (e.g., including masks to form a patterncomprising nanomaterials). In a further embodiment, each composition ornanomaterial can be applied to a single applicator one at a time inseparate application steps to provide the predetermined arrangement ofnanomaterial thereon.

When two or more nanomaterials, or two or more compositions, aretransferred in the desired arrangement from a transfer surface by asingle transfer step, the lateral offset of the patterns of thedifferent nanomaterials, or compositions, can be better-controlled thanwhen each of the different nanomaterials or compositions are transferredseparately. This can reduce or preferably eliminate variation fromprinting to printing. Expected registration accuracy and repeatabilitycan be better than 100 μm, as good as 1 μm, and eventually as good as 10nm with precise mechanical systems.

For example, the transfer surface can include a predeterminedarrangement of different compositions that include semiconductornanocrystals that emit light at different wavelengths. By including sucharrangement of semiconductor nanocrystals that emit light at differentwavelengths, a multicolor pattern can be formed on the applicator fordeposition onto the substrate.

Embodiments of the invention can also optionally include transferringmore than one layer simultaneously, for example a blanket deposited(unpatterned) layer of a first material (e.g., metal, metal oxide, etc.)can be applied to an applicator and a patterned second material (e.g.,semiconductor nanocrystals, etc.) applied thereto. Upon contacting theapplicator to the substrate, the patterned second material istransferred as well as the blanket of first material.

The method of the invention can optionally utilize various machinery andequipment of the pad printing industry. Such machinery and equipment canoptionally be manually operated, automated or semi-automated. An exampleof one manufacturer of such machinery and equipment is TOSH. Examples ofTOSH machines suitable for the present method include Logica 150, Logicami-microS, etc. However, other TOSH machines and equipment and machineryand equipment of other manufacturers may also be suitable. For furtherinformation concerning machinery and equipment, see, for example, JohnKaverman, “Pad Printing Technical Guidebook,” Second Edition (2002)Innovative Marking Systems, Inc. and Universal Pad Printing Guide(Machines Pads Inks Plates Tech Guide); Innovative Marking Systems; andwww.padprinters.com, the disclosures of which are hereby incorporatedherein by reference in their entireties.

Depending upon the nature of the nanomaterial and/or compositioncomprising nanomaterial being used, the nature of the substrate, and/orthe end-uses for an article or device including the depositedcomposition or nanomaterial, it may also be desirable to carry out themethod in a controlled environment, e.g., in a hood, glove box, under aninert atmosphere, under nitrogen, etc.

In certain embodiments, the transfer surface can be treated (e.g., byapplication of one or more coatings) or otherwise surface modified(e.g., chemical modification of the surface, energetic treatments(including, but not limited to, plasma treatment, laser treatment,etc.), or other suitable surface-modification techniques). A surfacetreatment can be applied to all or one or more portions of the surface.A surface treatment of the transfer surface can be included whether thesurface is featureless or whether the surface includes features (e.g.,one or more grooves). A surface treatment can include differenttreatments to different areas of the transfer surface. For example, thegrooves (e.g., the side walls and trough of the grooves) can receive onetype of surface treatment, and the top transfer surface (between thegrooves) can receive a different type of surface treatment. Thetreatments can be applied, for example, to alter the properties (e.g.,wetting attributes) of the transfer surface or portions thereof. Forexample, depending upon the wetting attributes of the composition andthe wetting attributes of the non-grooved surface of the transfersurface and/or the surface of the grooves, it may be desirable to alterthe surface energy of the non-grooved transfer surface and/or thesurface energy of one or more of the grooves. Such surface energymodifications can be made, for example, by including a coating on thesurface of the grooves of the transfer surface, on the non-groovedportion of the transfer surface, or both. Optionally, a first coating isapplied to the surface of the grooves and a second coating is applied tothe rest of the transfer surface, each coating material having eitherhydrophilic or hydrophobic properties, selected to reduce spreading.

Examples of various surface treatments that can be applied to thetransfer surface include trichlorosilanes, other silylation treatments,teflon, etc. Selection of other surface treatments can be readily madeby those of ordinary skill in the relevant art. In certain embodiments,silanized transfer surfaces can be preferred.

In certain embodiments, the surface energy of the groove surface can bemodified to enhance wettability of the groove surface so that thecomposition dispensed in the groove spreads within the groove.

Preferably, the surface energy of the non-grooved surface of thetransfer surface is modified to decrease the wettability so that thespreading of the composition on the non-grooved transfer surface isreduced, and preferably prevented. Modification of the non-groovedtransfer surface can reduce the transfer of pattern defects that canresult from the spread or other occurrence(s) of composition ornanomaterial on the non-grooved transfer surface at or prior to transferof the composition from the groove(s) to the applicator. Modification ofthe grooves can facilitate the spread of the composition within theentire groove to assist pick-up of the full groove shape and size.

Methods in accordance with certain aspects of the invention include useof an applicator. In certain embodiments, the applicator can have asurface that is featureless or smooth (e.g. without patterneddepressions and/or elevations). A featureless applicator surface can beplanar or contoured (e.g., convex, pyramidal, conical, etc.). In certainembodiments, the applicator surface can include features formed byelevations and/or depressions on the surface, e.g., a pattern ofelevations and/or depressions. The featured applicator surface canfurther be planar or contoured (e.g., convex, pyramidal, conical, etc.).Optionally, the surfaces of the individual features on the applicatorcan be planar or contoured. An applicator can further include acombination of one or more features with planar surface and one or morefeatures with contoured surface.

A contoured applicator can be useful for providing higher fidelityprinting and reduction of trapped gas (i.e. air, nitrogen) bubblesbetween the substrate and the applicator during the deposition of thepatterned nanomaterial.

Examples of an applicator can include, without limitation, a surface ofa stamp, a roller, a transfer tape, etc. Preferably, the applicator hasa predetermined dimension so that a pattern can be formed by one timetransfer, even, for example, in case of a display device having a largearea by using an applicator corresponding to a selected area of thedisplay device.

The applicator preferably has a configuration and dimensions selectedfor picking up the pattern formed from the filled transfer surfacegrooves.

The applicator can be configured to move or be moved relative to theposition of other components of the printing system being used, e.g.,the transfer surface and/or the uppermost surface of the substrate onwhich a nanomaterial or composition is to be applied. For example, theapplicator can be mounted on a drum, the drum being configured torotate. The surface of the applicator can be configured to roll on thesubstrate. The surface of the applicator includes an elevation or adepression, or the applicator can be substantially free of elevationsand/or depressions. The surface of the applicator can be configured tobe in continuous contact with the substrate.

In certain embodiments, the applicator can be a stamp.

The surface of the stamp can be planar or contoured (e.g., convex,angled, etc).

The surface of the stamp can be patterned (e.g., featured). A featuredstamp can be used, for example, with a smooth transfer surface whichincludes nanomaterial, A featured stamp can be used, for example, with atransfer surface including grooves (in which case, the raised featuresof the stamp preferably correspond (e.g., in size, shape, andarrangement) to the depressions of the transfer surface for efficientinking of the elevated stamp features).

The surface of the stamp can be smooth or featureless (e.g., an absenceof elevations and/or depressions of a pattern).

In embodiments in which the pattern to be applied onto the substrate iscontained on the transfer surface itself, the selection of the materialsand design (e.g., material, hardness, contour) of an applicator can beless restricted than when a patterned applicator is used to deposit apattern onto the substrate.

Mechanical limitations for a patterned-stamp are reduced or overcomewhen a pattern is formed on a featureless stamp. When a textured stampcontacts a substrate, any applied pressure (at least adequate to achievematerial transfer) is distributed in predictable but non-uniform ways.This induced stress can cause sagging of the stamp in the areas not incontact with the substrate surface. If the applied pressure is greatenough, the sagging areas can contact the substrate surface, resultingin material transfer in undesired regions. In contrast, pressure appliedto a stamp that is substantially free of elevations and/or depressionsleads to uniformly distributed forces over the stamped area, and thussagging and other non-uniform processes can be reduced or eliminated.

The stamp can be rigid or compressible.

The stamp can be constructed from a material which is elastomeric. Forexample, the stamp material comprises poly dimethyl siloxane (PDMS, forexample Sylgard 184), other silicone elastomers; and other elastomers.In certain embodiments, a material with low creep characteristics ispreferred.

A stamp comprising an elastomer material is particularly advantageousfor depositing nanomaterial comprising, e.g., semiconductornanocrystals, to a surface. The range of properties of various elastomermaterials facilitates selection of an applicator having a predeterminedhardness (durometer) which affects the force that can be applied as wellas the compression of the stamp.

A stamp can be prepared, for example, by preparing a silicon masterusing standard semiconductor processing techniques which define apattern on the silicon surface, for example a pattern of elevationsand/or depressions. Poly dimethyl siloxane (PDMS, for example Sylgard184) precursors are then mixed, degassed, poured onto the master, anddegassed again, and allowed to cure at room temperature (or above roomtemperature, for faster cure times). The PDMS stamp, having a surfaceincluding the pattern of the silicon master, is then freed from themaster, and cut into the desired shape and size.

Alternatively, for a non-patterned deposition, a stamp with a smoothplanar or contoured surface can be used. For example, a blankelastomeric master can be prepared, for example, by molding to a smoothplanar or contoured (e.g., curved) surface. Examples of smooth moldingsurface include, but are not limited to, optical glass lenses.

One can also utilize different elastomer molds to construct differentstamp profiles, realizing higher or lower stress on the surfacechemistry layer, depending on the application desired.

All of these mold shapes allow for the contact to be a single step orsequential steps. Preferably the entire applicator does not contact thesubstrate surface at once, but rather the highest point contactsinitially, and then only with compression does the rest of theapplicator make contact. This minimizes and more preferably prevents anyair or gas bubbles from getting trapped between the applicator and thesubstrate. Trapped air and/or gas bubbles can cause areas where notransfer occurs, and hence a void or defect in the pattern that isapplied to the substrate.

Alternatively, commercially available stamps can be used.

A preferred stamp is made from a material comprising a silicon basedelastomer (e.g., without limitation, PDMS) doped with a fluorinatedpolymer. In certain embodiments, the fluorinated polymer is included inthe material in an amount greater than zero up to at least about 0.1weight percent. In certain embodiments, the fluorinated polymer can beincluded in an amount of at least about 0.001 weight percent. The amountof fluorinated polymer dopant can be included in the stamp material upto an amount that is less than the amount at which the silicon basedelastomer including the fluorinated polymer dopant cannot be cured(e.g., forms an uncurable gel). In certain embodiments, the fluorinatedpolymer dopant comprises a fluoropolymer, a perfluorinated (completelyfluorinated) polymer, a partially fluorinated polymer, a polymer withperfluorinated alkyl substituents, a polymer with perfluorinated arylsubstituents, a polymer with partially fluorinated alkyl/arylsubstituents, a polymer with perfluorinated branched alkyl/arylsubstituents, a polymer with partially fluorinated branched alkyl/arylsubstituents, or a mixture of any two or more of the foregoing. Incertain other embodiments, the fluorinated polymer dopant comprises afluoropolysiloxane, a perfluorinated (completely fluorinated)polysiloxane, a partially fluorinated polysiloxane, a polysiloxane withperfluorinated alkyl substituents, a polysiloxane with perfluorinatedaryl substituents, a polysiloxane with partially fluorinated alkyl/arylsubstituents, a polysiloxane with perfluorinated branched alkyl/arylsubstituents, a polysiloxane with partially fluorinated branchedalkyl/aryl substituents, or a mixture of any two or more of theforegoing. Examples of fluorinated polysiloxanes include, but are notlimited to, Fluorogel™ Q3-6679 Dielectric Gel Part B and Fluorogel™Q3-6679 Dielectric Gel Part A, both available from Dow Corning. Incertain embodiments, the fluorinated polysiloxane is included in thestamp material in an amount from about 0.001 to about 50% by weight,from about 0.001 to about 10%, from about 0.5% by weight to about 5% byweight, from about 0.01 to 0.1% by weight. The stamping surface of astamp prepared from a silicone based elastomer including a fluorinatedpolymer dopant preferably does not further include a surface chemistrylayer or other surface treatment. The stamp can be prepared by knowntechniques. Preferably the fluorinated polymer dopant is included in thesilicone based polymer prior to molding the stamp material.

Optionally, a surface chemistry layer can be disposed over theapplicator. A surface chemistry layer can be applied by physical vapordeposition (PVD), chemical vapor deposition (CVD), or liquid or gasphase coating by a self-assembled monolayer, depending on the desiredmaterial surface properties.

The composition of the surface chemistry layer can be selected toreadily adhere and release the composition, in a wet transfer, ornanomaterial, in a dry transfer. The surface chemistry layer canoptionally act as a barrier to stamp swelling by the carrier medium forthe nanomaterial of the composition, and an adhesion/surface chemistrylayer for the composition or nanomaterial. Aromatic organic polymers,deposited by chemical vapor deposition, can be used as a surfacechemistry layer. See, for example, S. Coe-Sullivan, et al., AdvancedFunctional Materials, 15, 1117-1124 (2005), which is incorporated byreference in its entirety. Application of the surface chemistry layer bychemical vapor deposition can result in a conformal coating of theshaped stamp. The surface chemistry layer can be chosen to compatiblewith spreading of the composition which includes nanomaterial and aliquid. For example, with a liquid comprising chloroform, the surfacechemistry layer can be a chemical vapor deposited Parylene-C layer orother surface chemistry material. The Parylene-C layer can be, forexample, 0.1 to 2 μm thick, depending on the pattern to be reproduced.

Including a surface chemistry layer on the surface of an applicator canadvantageously enable complete release of the nanomaterial from thesurface thereof. For example, a surface chemistry layer comprisingParylene-C is compatible with a wide range of liquids (e.g., non-polarorganic liquids). Parylene-C is an aromatic polymer that can form thinand conformal coatings exhibiting highly inert properties.

The above properties of Parylene-C make it a suitable surface chemistrylayer for use in depositing nanomaterials comprising semiconductornanocrystals, particularly when deposited in thin layers including same.Optionally, a surface chemistry layer can include different parylenecompositions or other surface chemistry materials (e.g., but not limitedto, surface modifying organic molecules, plastics, and other surfacechemistry treatments known or identifiable by a skilled artisan in therelevant art for achieving the desired surface properties). Otherparylene materials that could be used in a surface chemistry layerinclude, for example, but are not limited to, Parylene, Parylene-N,Parylene-F, Parylene-D, Parylene-HT, Parylene AF4, etc. In certainembodiments, other surface treatments (e.g., energetic treatmentsincluding, but not limited to, plasma treatment, laser treatment, etc.)known or recognized in the art can be used.

In certain circumstances, a surface chemistry layer comprisingParylene-C may undergo as least partial delamination from PDMS. The canoccur for example, due to temperature effects (in light of thedifferences between the thermal coefficients of the two materials)and/or upon repeated application of pressure. Such delamination problemscan be reduced or avoided with use of surface chemistry release layercomprising organic molecular compounds. Such compounds can be includedin a surface coating on an applicator. Preferably the surface coatinghas a surface energy less than about 50 mJ/m², more preferably less thanabout 30 mJ/m², and most preferably less than about 20 mJ/m². In certainembodiments, the organic molecular compounds can be aromatic molecularcompounds. In other embodiments, the surface chemistry layer comprisesxxx-silanes. Such materials include functional groups that can bond withfunctional groups at the elastomer surface and self-align themselves onthe surface forming an organized coating. It is expected that thesematerials will remain immune to the dimensional changes in the elastomeroriginating from temperature variations or mechanical impact, and wouldmaintain its de-wetting function over extended period of time. Examplesof organic molecular compounds for inclusion in a surface chemistryrelease layer include, but are not limited to, aromatic organicmolecular compounds.

Other examples of compounds for inclusion in a surface chemistry releaselayer include, but are not limited to, ethyltrichlorosilane,ethyltriethoxysilane, n-propyltrichlorosilane, n-propyltrimethoxysilane,n-butyltrichlorosilane, n-butyltrimethoxysilane, n-hexyltrichlorosilane,n-hexyltrimethoxysilane, n-octyltrichlorosilane, n-octyltriethoxysilane,n-decyltrichlorosilane, n-dodecyltrichlorosilane,n-dodecyltriethoxysilane, n-octadecyltrichlorosilane,n-octadecyltriethoxysilane, n-octadecyltrimethoxysilane, water solubleoctadecylsilane, n-exosyltrichlorosilane, n-docosyltrichlorosilane,phenyltrichlorosilane, phenyltriethoxysilane,(tridecafluoro-1,1,2,2-tetrahydrooctyl)-1-trichlorosilane, and(tridecafluoro-1,1,2,2-tetrahydrooctyl)-1 triethoxysilane. In certainembodiments, the compounds can be hydrophobic.

In certain embodiments of methods in accordance with the invention, apreferred applicator comprises a coated stamp having a curved surfaceand a surface chemistry layer (e.g., Parylene-C or other surfacetreatment material) disposed thereon. For example, a curved Parylene-Ccoated stamp can deposit nanomaterial in a patterned or unpatternedlayer with improved uniformity and consistency.

In certain embodiments, a curved Parylene-C coated stamp is useful todeposit semiconductor nanocrystals from a composition also including anon-polar liquid or liquid mixture, especially when used in conjunctionwith commercially available machines, e.g., pad printers, that providecontrollable impact pressures.

The curvature of the stamp surface overcome the problems that can beencountered with flat surface applicators, e.g., trapped air bubbles,uncontrollable points of contact between stamp and substrate, andirreproducible or unknown pressure distributions of the stamp surface atimpact. As discussed above, these problems can deposit films withunpredictable quality and unpredictable consistency in area coverage andprinted film thickness.

A curved stamp provides a point of first contact with the substrate, aswell as control over that point. As pressure is increased on the stamp,the moving edge of contact is consistent and well defined, travelingcontinuously away from the initial point of contact. In addition, acurved surface stamp allows air to be squeezed out, so that bubbles arenot trapped between the stamp and substrate.

In certain embodiments, a stamp with a predetermined curvature can becreated by molding the stamp material with an optical lens having afocal length selected to obtain the predetermined stamp curvature.Examples of focal lengths useful for preparing stamps including aconvex-shaped surface useful for depositing nanomaterials include, butare not limited to, from about 10 mm to about 1,000 mm, from about 25 mmto about 500 mm, from about 100 mm to about 500 mm. In certain preferredembodiments, the focal length of the curvature is from about 15 mm toabout 350 mm, and more preferably from about 25 mm to about 300 mm. Inone embodiment, the diameter of the stamp surface is about 65 mm and thefocal length is about 244 mm.

The diameter of the lenses can be selected based on the size of the areato which nanomaterial is to be deposited. The focal length can beselected taking into account the diameter of the lens and the size ofthe substrate. Preferably, the lens is concave. More preferably, thelens is an optical quality plano-concave lens. The focal length of thelens will be the negative value of the focal length desired for thecurvature of the applicator surface. For example, an applicator with aconvex surface and a focal length of 25 mm can be prepared from aplano-concave lens with a focal length of −25 mm. In certainembodiments, the diameter of the optical lens is, for example, at least20% larger or, in other embodiments at least 30% larger, than thediameter or diagonal of the area to which nanomaterial is to bedeposited.

This step is followed by the standard curing and coating procedures.Different curvatures allow for variability in pressure distributions atimpact, speed of the moving contact line, inkability, and surface areaof resulting film. Preferably, the mold used to form the curved surfaceof the stamp is optically smooth. The smoothness of the mold can improvethe flatness of deposited layers of nanomaterials, e.g., semiconductornanocrystals, at monolayer thicknesses. In certain embodiments, the Λ orsmoothness rms of the stamp surface is less than about 5 nm.

Alternatively, the applicator can be the surface of a roller. In certainembodiments, the dimensions of the roller can be selected correspondingto the dimension of the substrate. For example, the roller can have awidth that is substantially the same as that of a surface (e.g., a panelof a display device to be fabricated) and a circumference having thesame length as that of the surface. In such example, the compositionfilled in the groove of the transfer surface can be transferred to acircumferential surface of the transfer roller and deposited onto thesubstrate by a one time rotation. In other embodiments, other sizerollers can be selected. Depending on the sizes of the roller andsubstrate, deposition may include less than one or greater than onerotation of the roller across the substrate surface.

As the transfer roller is rotated in a state of being in contact withthe surface the predetermined pattern comprising nanomaterial is formedon the substrate. At this time, depending upon the size of the rollerand substrate, it is possible to form the predetermined pattern over theentire substrate of, for example, the display, by one rotation of thetransfer roller.

For example, if the transfer surface and the transfer roller can befabricated according to the size of the substrate deposition region, thepattern can be formed thereon by one transfer, thereby enablingformation of a pattern having a large area just by one event ofprocessing.

This embodiment has many advantages. Particularly, the predeterminedpattern comprising nanomaterial can be deposited onto the substratehaving a large area by one-time processing and a pattern more complexthan a pattern using conventional photolithography processing can beformed.

In FIG. 3 A, the applicator is, by way of example, a roller 325 that maybe rolled across the uppermost surface 323 of the transfer surface alonga first direction so that the one or more compositions contained in theplurality of grooves of the transfer surface are temporarily bonded ontothe surface 328 of roller 325. Accordingly, the pattern comprising thecomposition-filled grooves 326 is transferred onto the applicator.

When transfer of the pattern features 324 onto the roller 325 iscomplete, the transfer surface may be refilled or cleaned and refilled.

In FIG. 3 B the roller 325 with the composition pattern 324 may bepositioned above a substrate 310. The roller may roll across thesubstrate thereby transferring a pattern 324 of nanomaterial from theroller onto the substrate (e.g., the uppermost surface of a substratewhich may optionally include one or more layers of a structure.)Accordingly, the pattern of the filled grooves 326 (in FIG. 3 A) istransferred onto the substrate. The substrate 310 including the pattern324 of one or more nanomaterials may subsequently undergo additionalprocessing.

If a dry transfer is desired, for example, after the predeterminedpattern comprising the composition is applied to the applicator, thepatterned composition is permitted to dry so that when the applicator iscontacted to the substrate, patterned nanomaterial is transferred to thesubstrate.

Preferably the applicator is contacted to the surface of the substrateunder conditions to cause at least a portion of the nanomaterialincluded on the applicator to be deposited onto the substrate Forexample, in certain embodiments, the applicator can be contacted to thesubstrate at a pressure of at least 0.1 lb/in² for at least a period oftime effective for transferring at least a portion of the nanomaterialonto the substrate, e.g., thirty seconds or less. In certainembodiments, for example, the pressure is at least 1 lb/in², but lessthan 50 lb/in². In certain other embodiments, for example, the pressureis in the range from about 100 lb/in² to about 500 lb/in² In certainother embodiments the pressure is less than the pressure at which thefilm or substrate is damaged.

The surface details (e.g., featured or featureless), shape (e.g., planaror contoured, etc.), dimension, and hardness of the applicator areselected based upon the particular composition (e.g., the weight %nanomaterial in the composition, the liquid, any other optionalcomponents), the contemplated end-use application, the substrate, etc.These various aspects of the applicator surface can be readily selectedand determined by a person of ordinary skill in the art.

One or more compositions including one or more nanomaterials can bedelivered to a transfer surface by various techniques. For example, thecomposition(s) can be dispensed from an inkcup, a micro-dispenser (e.g.,a needle, inkjet print head, nozzles, syringe, etc.), an array ofmicro-dispensers (e.g., an array of needles, an array of multiple inkjetheads, an array of nozzles, misters, and array or syringes, etc.) thatare movably mounted to be positioned over and aligned with the locationon the transfer surface to which one or more compositions are to bedispensed. Preferably, a predetermined metered amount of a compositionis dispensed. Techniques for delivering or dispensing composition to atransfer surface will be discussed further below. Optionally, variousmasking techniques can be further included with techniques fordelivering or dispensing a compositions selectively to a transfersurface.

For example, one or more compositions can be dispensed to one or moregrooves of the transfer surface by various techniques, including, butnot limited to, use of an inkcup or from a micro-dispenser or an arrayof micro-dispensers (e.g., needles, inkjet nozzles, misters, etc.)positioned over and aligned to dispense a metered amount of compositioninto each groove to be filled.

An inkcup technique can be particularly useful for dispensing thecomposition into transfer surface grooves. Any type of inkcup can beused, for example, an open inkcup, a closed inkcup, or a pressurizedinkcup.

In an open inkcup, the content is confined in a well that is open to theatmosphere. Depending on the properties of the content, the content ofan open inkcup can experience variations in concentration and viscositycaused by evaporation. Such variations can affect the quality of thepattern of nanomaterial that is deposited onto the substrate.

In a closed inkcup, the content is confined in a well that is closed tothe atmosphere, so variations to the content that can result fromevaporation are reduced or eliminated. For this and other reasons, aclosed inkcup is preferred. A closed inkcup can be positioned upsidedown and slide over the transfer surface or the transfer surface mayslide over the inking surface of the inkcup. The latter approachrequires the inkcup to be pressurized. A pressurized inkcup typicallyincludes a diaphragm that supports the ink well and can be raised to wetthe transfer surface pattern and then retracted.

The pressurized ink cup can be particularly useful when printing has tobe done on the surfaces that are not horizontally positioned relative tothe inking surface of the inkcup.

With a closed inkcup system, the composition to be dispensed is confinedwithin the ink-cup. The edge of the inkcup that is in contact with thetransfer surface during the dispensing of the composition is sometimesreferred to as a doctor ring. This edge in contact with the transfersurface forms a seal with the transfer surface. In certain embodiments,the seal can be improved by application of pressure. The seal betweenthe inkcup edge and the transfer surface depends upon the flatness ofthese parts and also on surface finish of each. When an inkcup is usedto dispense the composition, the area of the transfer surface containingthe grooved pattern is preferably planar and preferably smooth.

The sealing force between the ink-cup and surface of the transfersurface is also dependent on the mass of the inkcup and any additionalpressure applied to the inkcup when contacted to the transfer surface.Optionally, the seal between the inkcup and surface of the transfersurface can be further reinforced by, for example, a magnetic forceoriginated by magnets located within the body of the ink-cup and undertransfer surface that is magnetic, e.g., a steel plate.

Inkcups can be used with compositions of having viscosities, forexample, from greater than about 1 cP to about 20 cP, less than about 1cP, greater than about 20 cP, etc.

The edge of the inkcup that is in contact with the transfer surface actsas a doctor blade. When the inkcup is moved across the transfer surface,the composition is filled into the grooves over which the inkcup ismoved, and the composition which remains at the surface of the transfersurface between the grooves is removed. The use of an inkcup allows fora high degree of flexibility and control over how to introduce thecomposition to the inkcup.

Manipulation of pressure (e.g., by vacuum (e.g., within the inkcup) orpositive pressure) allows the control of leakage of low viscosity inksfrom the transfer surface/inkcup assembly, as well as control ofconcentration variations that could be associated with any such leakage.

When two or more different compositions are to be dispensed into certaintransfer surface grooves, they are preferably dispensed from an inkcupone composition at a time.

Preferably, a tight seal is maintained between the portion of the inkcup(e.g., doctor ring) in contact with the transfer surface and thetransfer surface itself to confine the composition within the cup. Thiscan be particularly useful when the composition includes a carriermedium having a low viscosity liquid. More preferably, the portion ofthe inkcup in contact with the transfer surface comprises asubstantially smooth, planar finish.

Optionally, the surface energy of the portion of the inkcup in contactwith the transfer surface can be modified to increase the dewettingcharacteristics thereof with respect to the composition being dispensedby the inkcup. Such modification of the inkcup can assist in reducingthe possibility of leakage of the composition through any surfaceimperfections at the seal between the inkcup and the transfer surface sothat the composition preferably remains confined within the cup whenmoving across the transfer surface until deposited in the grooves of thetransfer surface pattern.

The surface modification of the inkcup edge can optionally be utilizedwith one or more surface energy modifications of the transfer surface(s)discussed above. It is believed that any such surface modifications,alone or in combination, can extend the range of liquid viscosity tolower values, and improve uniformity of transferred patterns.

Most preferably, the mating seal counterparts, the doctor ring, andtransfer surface are free of surface defects such as cracks, grooves,indentions, or even micro scale damage to prevent leakage of thecomposition.

The edge of the inkcup in contact with the transfer surface and/or thenon-grooved surface of the transfer surface are optionally planarizedand/or polished to reduce, and preferably, eliminate defects that canresult in leakage of composition from the mated surfaces while thecomposition is being dispensed into the grooves.

Optionally, these two surfaces comprise materials with differenthardnesses, such as, for example, a cliché comprising steel and aninkcup with an edge comprising a ceramic material that is softer thanthe steel used to fabricate the cliché. Various other materials ofconstruction and/or their combinations, such as various ceramics,ceramic coating, glass, metals, or silicon may alternatively beutilized, for the transfer surface and inkcup edge.

An inkcup can be used in a static fashion, where the cup is filled,sealed, and not tampered with through successive prints. Alternatively,a flow system can optionally be utilized to reflow the composition fromthe inkcup to a reservoir, thereby maintaining and stabilizing thecomposition concentration and viscosity. The composition in a reflowloop may further optionally be monitored for concentration (via variousoptical means, for example) and the concentration maintained actively byaddition of controlled quantities of carrier medium or concentratedcomposition or nanomaterial into the reflow loop to lower or raise theconcentration of nanomaterial in the composition.

Another technique that is particularly useful for dispensing one or morecompositions (e.g., different colored compositions) onto a transfersurface includes use of a micro-dispenser or an array ofmicro-dispensers (e.g., needles, inkjet nozzles, etc.) positioned overand aligned to dispense such composition or compositions thereto. Incertain embodiments, the transfer surface includes one or moredepressions (e.g., grooves, recessed wells, etc.), in which case, themicro-dispenser or array of micro-dispenses can be aligned to deliverthe composition(s) into the individual grooves. Such micro-dispenserscan optionally deliver different compositions to the transfer surfacesimultaneously or sequentially.

When the composition is dispensed from one or more micro-dispensers togrooves of a transfer surface, the transfer surface grooves can befilled by moving the transfer surface relative to the micro-dispenser(s)or alternatively, the micro-dispenser(s) can be moved relative to thegrooves of the transfer surface, with the moving component being stoppedat intervals selected to permit filling of unfilled grooves until all ofthe grooves are filled.

A micro-dispenser can be used to fill each of the grooves with the samecomposition. Two or more different compositions can be dispensed intothe transfer surface grooves by sequential delivery of each compositionfrom a micro-dispenser. Two or more different compositions can bedispensed into the transfer surface grooves non-sequentially. Forexample, an array of multiple micro-dispensers, e.g., an ink jet systemhaving multiple print heads, can dispense different nanomaterials in anon-sequential manner. An array of micro-dispensers can also beprogrammed to dispense compositions into the grooves sequentially or inaccordance with another predetermined order based on the pattern, groovelocation, dimensions of the transfer surface, etc.

FIG. 4 depicts a schematic of an example of a system including an arrayof micro-dispensers for dispensing one or more compositions into groovesof a cliché. The cliché 450 includes a predetermined pattern of groovesin the upper surface 455 thereof. An array micro-dispensers 410 isdisposed over the cliché to dispense compositions into the grooves. Atdispensing time, each micro-dispenser is aligned with the groove intowhich a given composition is to be dispensed.

FIG. 5 depicts a schematic of example of a system for dispensing morethan one composition into grooves of a cliché. The system includes anarray of micro-dispensers that are spatially arranged for dispensingcompositions into the predetermined pattern formed by the array ofgrooves on the transfer surface. Optionally, micro-dispensers can bepositioned along a dimension (e.g., length, width, diagonal, etc.) ofthe cliché. Optionally, the individual micro-dispensers of an array canbe arranged in a linear arrangement, but the arrays are positioned abovethe transfer surface at an angle to allow dispensing compositions intoclosely spaced grooves. Alternatively, a linear array of microdispensersare positioned above transfer surfaces that are disposed on an angle.Other configurations of the transfer surface grooves and the array ofmicro-dispensers are possible. The relative placement of themicro-dispensers corresponds to the pattern of the cliché so that when acomposition is dispensed into a groove, the dispensed composition willspread in or wet a groove of the cliché due to surface tension andgravity. Subsequent to filling a groove, the micro-dispenser can bemoved to be positioned over the next groove to receive the samecomposition. The micro-dispenser array will continue to move over thearea of the pattern dispensing the composition in a continuous mode orby multiple injections. A second micro-dispenser array will similarlydispense a second composition into the appropriate grooves in accordancewith the predetermined pattern.

After the grooves are filled with the one or more different compositions(e.g., three different compositions, each respectively comprising, e.g.,blue-emitting, green-emitting, and red-emitting semiconductornanocrystals (also referred to as quantum dots (abbreviated as “QD” inFIG. 5)), the predetermined pattern is picked-up by the applicator andthe pattern can thereafter be applied to the substrate.

Preferably, one or more compositions or nanomaterials are deposited ontoa substrate in a single deposition step. This single transfer processreduces and preferably eliminates variations in the concentrations ofnanomaterial in the composition during the deposition of the pattern tothe substrate.

This preferred embodiment method can include a featureless applicator ora featured applicator.

In an embodiment including an applicator with a featureless surface(e.g., a stamp or roller with a surface that is substantially free ofelevations and/or depressions), the applicator surface can be patternedby contact with a cliché to transfer multiple compositions ornanomaterials to a substrate, rather than using a separate stamp foreach different composition or nanomaterial.

In an embodiment including a featured applicator surface, the featuresof the applicator are aligned with a transfer surface which includes apattern of grooves arranged and sized to receive the features of thepatterned applicator. To apply a composition or nanomaterial to a stampfeature, the stamp features are contacted to compositions ornanomaterials included in corresponding grooves. The stamp featurespick-up the predetermined composition(s) for application of the patternto the substrate.

The use of a single deposition step to transfer a complete pattern ormultiple components of a pattern avoids the need to register subsequentstamps to the previously deposited patterns. Further, by reducing thenumber of instances of contact between the applicator and the substrateto which nanomaterial has been previously applied, the possible damageto, or disruption of, the previously applied nanomaterial is reduced.For example, in depositing a pattern comprising different colornanomaterials comprising semiconductor nanocrystals to a substrate, asingle step transfer reduces the risk of damage to the patternednanomaterials. This can be particularly advantageous when thenanomaterials are applied in thicknesses of several monolayers or less.

FIGS. 6A-6D provide a schematic of an example of the steps involved in asingle transfer of more than one different color nanomaterials. In StepA (FIG. 6A), more than one composition is dispensed into the grooves(not shown) in an upper surface of a transfer surface. In certainembodiments, multiple compositions can be dispensed frommicro-dispensers disposed over the transfer surface in an array. Each ofthe micro-dispensers can dispense a composition at the same or differenttimes. Optionally, the transfer surface can be moved under a positioneddispenser or micro-dispenser array, the dispenser or micro-dispenser canbe moved over a positioned transfer surface, or the transfer surface andarray can each be moved into alignment at or prior to the time thegrooves are filled.

To transfer a pattern comprising different nanomaterials in a singletransfer step, all of the various compositions including the differentnanomaterials to be deposited are dispensed into the patterned groovesbefore the applicator is contacted to the transfer surface.

For example, an applicator is contacted to the transfer surface andseparated therefrom to form a pattern on the surface of the applicator(Step B (FIG. 6B)).

If a dry transfer is desired, for example, the transfer surface is notcontacted to the substrate until any liquid component of thecomposition(s) evaporates from the transfer surface, leavingliquid-free, or substantially liquid-free, nanomaterials on the transfersurface. As discussed above, a substantially liquid-free transferincludes, for example, no more than about 10 parts per hundred liquid,preferably no more than about 10 parts per thousand liquid, and morepreferably no more than about 10 parts per million liquid.

The applicator surface including the pattern is contacted to thesubstrate to deposit the pattern thereon (Step C (FIG. 6C)) andthereafter separated therefrom (Step D (FIG. 6D)).

By depositing more than one nanomaterial onto the substrate in a singletransfer, better control of the concentration of the composition can bepossible. Additionally, cleaning steps between separate transfers ofdifferent nanomaterials can be avoided.

As discussed herein, the ability to transfer a pattern comprising morethan one nanomaterial by a single transfer further avoids the need toregister the alignment of successive transfers of separate transfers ofeach individual nanomaterial and eliminates the need to index successivetransfers of each individual nanomaterial. Scale-up can also befacilitated.

Another technique for depositing a pattern comprising nanomaterial ontoa substrate includes the use of a tape. The tape can act as a donorsurface for depositing nanomaterial onto a substrate or onto a temporarytransfer surface. FIG. 7 depicts the relative arrangement of a tape andsubstrate to receive the deposited composition(s) or nanomaterial(s). Inthe example shown, the tape is contacted to the substrate with use of apresser (depicted in the illustrated example as a stamp). In the exampleshown in FIG. 7 the presser comprises a roller with a circularcross-section. Alternatively, a roller with an oval cross section, astamp, or other device suitable for depressing the tape against thetransfer surface and/or substrate may optionally be used.

Other techniques, methods and applications that may be useful with atape including nanomaterial disposed thereon are described in U.S.Provisional Patent Application No. 60/790,393, entitled “Methods AndArticles Including Nanomaterial”, of Seth Coe-Sullivan, Maria J. Anc,LeeAnn Kim, Vladimir Bulovic, loannis Kymissis, John E. Ritter, andRobert Praino, filed by Express Mail on 7 Apr. 2006, the disclosure ofwhich is hereby incorporated herein by reference in its entirety.

FIG. 9 provides a schematic example of a system including a tape fordepositing nanomaterial onto a substrate.

Referring to FIG. 9, the deposition of one or more nanomaterials onto asubstrate is facilitated by pick up of a composition comprisingnanomaterial, unpatterned or in a predetermined pattern, from a transfersurface (e.g., a cliché system as depicted) onto a surface of the tape92 which is run through the system. The nanomaterial is subsequentlytransferred to the substrate 98. A presser 94 (examples of which includea roller (having e.g., circular or oval cross-section) or a stamp(examples of which are depicted in FIG. 8) or other suitable componentmay be used to press the tape against the transfer surface and/or topress the tape against the substrate. The presser and tape act as anapplicator to deposit nanomaterial onto the substrate.

Optionally, the tape and presser can be selected to have dimensionsselected such that the substrate can be fully patterned in a singleprocess step.

The tape can optionally be a consumable or can be recycled. If recycled,the tape will preferable be clean before being reused. Optionally, thismethod can carried out in a continuous manner (e.g., roll to roll).

An embodiment of the invention including a tape can optionally furtherinclude a release layer or other surface treatment of the tape surface,tape dispensing components, post-use conditioning of the tape (dry orwet cleaning), etc.

In embodiments including deposition of a predetermined patterncomprising one or more different nanomaterials, the number, arrangement,shape, and size of the grooves of the transfer surface and thenanomaterials included therein will be selected according to thepredetermined pattern to be deposited onto the substrate. The one ormore compositions comprising the nanomaterials to be deposited can bedispensed into the grooves by any of the above-discussed techniques orother suitable techniques for dispense compositions and/or nanomaterialsonto a transfer surface.

The use of a tape to deposit nanomaterial onto the substrate is expectedto deposit nanomaterial(s) onto the substrate with improved resolution(e.g., fewer distortions in the applied pattern). A method utilizing atape to deposit nanomaterial(s) onto the substrate is expected toprovide increased scalability with respect to the sizes of thesubstrates to be patterned and also the number of surfaces to beprocessed per unit time.

Preferably the tape has sufficient thickness and/or rigidity to receivethe composition, transfer the composition or nanomaterial, and bemanipulated by the presser and tape handling components of theequipment. Examples of tape materials include, e.g., PET, Kapton,plastic, foil, paper, nylon, cloth, etc. The tape preferably has arelease layer deposited on the face that will pick up the compositionand deposit the composition and/or nanomaterial composition onto thesubstrate, depending on whether a wet or dry transfer is desired.Examples of a coating include, Parylene, Parylene-C, Parylene-N,Parylene-F, Parylene-D, Parylene-HT, Parylene AF4, other parylenecompositions, other surface modifying organic molecules, and otherplastics, and other surface chemistry and/or other surface treatments(e.g., energetic treatments including, but not limited to, plasmatreatment, laser treatment, etc.) known or recognized in the art. Incertain embodiments, the surface can be silanized.

If a coating or release layer is included on the tape, deterioration(e.g., abrasion-wear, flaking due to brittleness, etc.) of the integrityof the layer (e.g., the integrity of the attachment of the layer to thetape, smoothness of the layer, etc.) can be reduced by adjusting theshape and contour of the presser (e.g., the radius of curvature of astamps, the radius of curvature of the rollers, the tape path itself,etc.).

In certain embodiments, the surface of the tape can be smooth (e.g., itdoes not include elevations and/or depressions). In other embodiments,the surface of the tape can include features (e.g., elevations and/ordepressions).

As in the other embodiments discussed above, preferably a presser is nota flat surface that fully presses the tape against the substrate at asingle time, to minimize trapped air between the tape and substrate whenthe composition or nanomaterial, as the case may be, is applied. Trappedair during the deposition step can result in an incomplete transfer.

Using a pick-up rate and deposition rate that are the same can result inineffective transfer of the nanomaterial to the substrate in when a tapeand presser comprising a roller are used. It is expected that a moreeffective transfer can occur when the two rates are different. SeeMatthew A. Meitl, et al., “Transfer Printing By Kinetic Control OfAdhesion To An Elastomeric Stamp”, Nature Materials 5, 33-38 (1 Jan.2006) Letters, the disclosure of which is hereby incorporated herein byreference in its entirety.

Referring to FIG. 10 A, one or more compositions are delivered to theuppermost surface of a transfer surface from above (by, e.g., an inkcup,a micro-dispenser, an array of micro-dispensers, etc.) or from below thetransfer surface (by, e.g., use of a transfer surface with a reservoirbelow and in connection with the uppermost surface of the transfersurface).

Referring to FIG. 10 B, a tape is passed over the uppermost surface of atransfer surface including at least one composition. A first presser(depicted as a roller with a circular cross-section) rolls over the sideof the tape remote from the transfer surface to press the underside ofthe tape (as depicted) against the uppermost surface of the transfersurface to transfer composition from the transfer surface to the tape.Referring to FIG. 10 C, the tape is advanced to align the composition onthe tape for application to the substrate upon contact when pressed by asecond presser (FIG. 10 D).

If a dry transfer is desired, for example, after the predeterminedpattern comprising the composition is applied to the tape, the patternedcomposition can be permitted to dry so that when the second presserpresses the tape including the pattern against the substrate, patternednanomaterial is transferred to the substrate.

While both depicted as rollers, the first and second pressers can havethe same or different shapes and/or sizes. It is envisioned that asingle presser could be moved relative to the tape, transfer surface,and substrate instead of using two applicators. Optionally the surfaceof the applicator(s) used can be patterned or featureless.

Alternatively, an unpatterned layer of one or more nanomaterials can betransferred to a tape from a smooth transfer surface and deposited ontothe substrate by contacting the tape to the substrate.

FIG. 11 illustrates an alternative embodiment in which one or morecompositions are delivered to a surface of the tape by inkjet printing.When a composition is used which includes a carrier which dissolves orotherwise reacts with the substrate, the use of inkjet printing todeliver the composition to the surface can reduce or remove theconsiderations of such reaction provided the vapor pressure of thecarrier and/or ambient conditions facilitate evaporation of the carrierprior to transfer of the nanomaterial to the substrate.

While FIGS. 10 and 11 depict examples of embodiments that include aroller, a stamp or other device could alternatively be used to contactthe tape to the transfer surface and/or the substrate.

FIG. 12 illustrates an example in which the deposition process isembodied in a continuous line. The belt 1230 moves in a direction (shownby the arrow). A substrate, for example, a display panel, 1220 iscarried on and moved in the same direction as the belt movement in acontinuous line for fabricating, e.g., a light emitting device includingsemiconductor nanocrystals.

As shown, the transfer surface comprises a transfer surface 1200 that isformed in the shape of a cliché roller. The transfer surface is incontact with the applicator 1210. As the belt 1230 progresses, thesubstrate 1220 progresses to be placed in contact with the applicator1210 and the applicator 1210 is rotated with a speed corresponding to aprogression speed of the belt 1230. In the meantime, the transfersurface 1200 is also rotated with the rotation of the applicator 1210,so that the composition 1204 from the transfer surface 1200 istransferred to the applicator surface 1210 and thereafter compositionsor nanomaterials (depending on whether the conditions and time areselected to achieve a wet or dry transfer, respectively) 1222 aredeposited on the substrate 1220. The composition can be dispensed to thetransfer surface from a micro-dispenser (as shown), from an array ofmicro-dispensers, or other known techniques.

When deposition onto one substrate is finished, a next substrate can beplaced on the belt for contact by the applicator and the same processesare repeated, thereby depositing a pattern on a plurality of substratesby consecutive processes.

The substrate including the deposited nanomaterial 1222 can betransported to a subsequent line for subsequent processing.

Optional additional steps can be included in the method. Optionally,patterned or unpatterned nanomaterial can be deposited onto thesubstrate.

Alternative techniques can be used for depositing one or morecompositions onto the tape include silk screening, etc.

Various aspects of the present invention will be further clarified bythe following examples, which are intended to be exemplary of thepresent invention.

Example 1 Printing Of 400 um Lines Comprising Semiconductor NanocrystalsUsing TOSH Logica 150 Utilizing A Wet Transfer Pad Printing Process

The process described in this example can be useful for printingdirectly on a substrate (that may include other layers or materials) oron a transfer surface or donor sheet for subsequent dry transfer.

Clichés: Standard pad printing etched polymer clichés can be used. Incertain embodiments for depositing repeating patterns of two or moredifferent nanomaterials (e.g., semiconductor nanocrystals), a separatecliché is preferably used for each different nanomaterial to bedeposited on a substrate. For example, to print a repeating pattern ofthree different semiconductor nanocrystals for emitting red, green, andblue light, respectively, three different clichés are preferably used,one for each color. An example of a cliché pattern useful for printingrepeating patterns of red, green, and blue, to print pixels for adisplay, includes a 400 um line geometry with 1500 um pitch. To createsuch clichés, the plates are exposed through a 150 dpi/90% line screento produce a controlled etch depth of approximately 30 um.Stamps. A stamp geometry with an 80 mm diameter contact area and 150 mmcurved radius can be used with the above clichés. A standard padprinting industry silicone resin is used to cast the stamps having aShore A durometer rating of 70.Inks: Printing inks comprising semiconductor nanocrystals including acore/shell structure, size, and chemical compositions capable ofemitting a desired color are dispersed in about 5 ml of nonane with nofurther dilution. 1 to 2 ml of ink is dispensed into standard padprinting ink cups.Printing Process The standard pad printing process to print a pattern oftwo, e.g., red and green, inks is carried out as follows:

-   -   1) A cliché pattern for each of the two colors to be printed is        filled simultaneously with ink by ink cups at each printing        station of the TOSH Logica 150.    -   2) Ink cups are retracted and a cliché pattern is picked by each        of the stamps from the respective cliché    -   3) A first stamp transfers, e.g., red ink, to the substrate        first.    -   4) The substrate moves to the second, e.g., green position, and        a second stamp transfers green ink to the substrate.        Process Parameters The process parameters for the printing        equipment are determined based on the viscosity and volatility        of the ink to be printed. The equipment printing parameters for,        e.g., TOSH Logica 150, are based on an arbitrary scale of 1 to 5        (1 slowest, 5 fastest) and time delays measured in seconds. In        general, parameters relating to pick up from the cliché can have        a stronger effect on print quality than transfer parameters. In        particular, for a nonane based ink, the time delay down on the        cliché can have a strong effect on print quality. A delay down        on the cliché allows liquid component of the ink in the cliché        to be absorbed into the stamp. This modulation of the volume of        the liquid component allows control of line uniformity and ink        spreading on the stamp.

Machine Parameter Setting/Time Machine Setting SelectionConsideration(s) Pick up Cliché impact speed 1 Slow to preventdisturbance of ink in cliché This parameter can strongly affect printquality. Time delay down on cliché 30 sec Long delay times allow liquidcomponent of the ink to be absorbed into the stamp. This control of theliquid component can improve print quality. Speed up from cliché 5Maximized to prevent ink spreading before transfer Delay before transfer0 Minimized to prevent ink spreading before transfer Transfer Transferimpact speed 1 Found to have weak effect on print quality Time delaydown on 10 sec Interaction with time delay down on cliché. Longsubstrate delay times slightly improve print quality when coupled withlong cliché delay times Speed up from substrate 5 Slight improvement inprint quality at high speeds

Example 2 Printing Semiconductor Nanocrystals Using TOSH mi-microSUtilizing A Dry Transfer Pad Printing Process

The process described in this example can be useful for printingdirectly on a substrate (that may include other layers or materials) oron a transfer surface or donor sheet for subsequent dry transfer.

A monolayer of semiconductor nanocrystals (capable of emitting red lightupon excitation) is formed on a piece of silanized glass. The monolayeris formed by dispensing 220 micro-liters of a dispersion ofsemiconductor nanocrystals (having an optical density of 0.011) inhexane from a micropipette to a piece of silanized glass mounted in aspinner. The spinner settings are set at 3000 speed/5000 ramp/60seconds. Immediately after dispensing the semiconductor nanocrystaldispersion, the spinner is started.

Silanizing can be carried out by known techniques. One techniqueinvolves first treating the substrates to be silanized with O₂ plasmafor 5 minutes and immediately thereafter rinsing with deionized (DI)water for about a minute, to obtain a clean hydrolyzed substratesurfaces. A beaker including a mixture of 70 ml hexane, 10 ml CCl₄, and2 ml (2 CHCl₃:3 CCl₄)H₂O is placed in a sonicator including a ice/watermixture having a temperature <10° C. 200 μL of tichlorosilane is thenadded to the beaker. The clean substrates are loaded into a substratecarrier and placed in the beaker. The contents of the beaker issonicated for about 24 minutes. After sonication, the substrate carrieris removed from the beaker. The substrates are thereafter removed andrinsed with chloroform then DI water (or alternatively chloroform, thenacetone, then methanol (then water—especially effective on a hydrophicsilane), and thereafter blown dry with nitrogen

After spin-coating, the silanized glass including the spin-coatedsemiconductor nanocrystal layer is positioned in a TOSH mi-microS modelpad printer at the location where the stamp would normally contact thecliché. An organic substrate (e.g., including a 50 nm thick layer ofE105 on PEDOT-coated plain glass) is positioned in the pad printer atthe location where the stamp makes print contact to the surface to beprinted. A lens molded stamp (that can be prepared as generallydescribed above and including a layer of parylene) is mounted in the padprinter, and semiconductor nanocrystals are printed from the silanizedglass to the top of the organic substrate. Increases in contact times ofthe stamp with semiconductor nanocrystal coated glass when picking upsemiconductor nanocrystals and of the stamp with the organic substratewhen depositing or printed dots can improve transfer efficiency.

Methods in accordance with the invention provide advantages that can beparticularly useful, for example, in depositing semiconductornanocrystals in the fabrication of a light-emitting device (LED)including semiconductor nanocrystals.

As discussed above, in certain embodiments, the method of the inventioncan allow the patterned deposition of solution processable layerscomprising nanomaterial (e.g., semiconductor nanocrystals, othernanoparticles, etc.) within a layered structure without disturbing thestructure fidelity through the introduction of solvent to the device.

In addition, certain embodiments of the invention can be useful withexisting backplane technology, and with off-the-shelf well knowntransport films.

The present invention is also expected to facilitate high throughput,since the nanomaterial can be introduced to the device in an singularprocess. Various embodiments of the invention are also expected to becompatible with processes for the manufacture of flexible displays,whether, for example, by roll-to-roll or flex-on-rigid batch modeprocessing.

Because semiconductor nanocrystals have narrow emission linewidths, arephotoluminescent efficient, and emission wavelength tunable, they can bea desirable lumophore. The semiconductor nanocrystals optionally includeorganic ligands attached to the surface thereof. These zero-dimensionalsemiconductor structures show strong quantum confinement effects thatcan be harnessed in designing bottom-up chemical approaches to createcomplex heterostructures with electronic and optical properties that aretunable with the size and composition of the nanocrystals.

The size and composition of the semiconductor nanocrystals can beselected such that semiconductor nanocrystals emit photons at apredetermined wavelength of wavelength band in the far-visible, visible,infra-red or other desired portion of the spectrum. For example, thewavelength can be between 300 and 2,500 nm or greater, such as between300 and 400 nm, between 400 and 700 nm, between 700 and 1100 nm, between1100 and 2500 nm, or greater than 2500 nm.

The semiconductor nanocrystals can include semiconductor nanocrystalsthat emit light at the same or different wavelengths. By including anarrangement the semiconductor nanocrystals that emit light at differentwavelengths, a multicolor pattern can be formed.

For example, a multicolor pattern can optionally include a repeatingpattern comprising two or more different semiconductor nanocrystalmaterials that emit light at different wavelengths.

When two or more different color emitting compositions includingnanomaterial are included as an emissive material of a display, eachdifferent color emitting nanomaterial can each independently include aplurality of semiconductor nanocrystals.

The method can include introducing onto a transfer surface a firstnanomaterial including a plurality of semiconductor nanocrystals havingan emission wavelength distinguishable from a second nanomaterialincluding a plurality of semiconductor nanocrystals.

The method can further include introducing a third or morenanomaterials, each including a plurality of semiconductor nanocrystals,on a transfer surface. Each of the third or more nanomaterials comprisesa plurality of semiconductor nanocrystals that can have an emissionwavelength distinguishable from that of the other nanomaterials. Thefirst, second, third, and other nanomaterials including pluralities ofsemiconductor nanocrystals can be applied to the same or differenttransfer surfaces, in either case, to be deposited in overlapping ornon-overlapping predefined regions of the substrate. The emissionwavelengths of the first, second, third, and other nanomaterialscomprising pluralities of semiconductor nanocrystals can be selectedfrom an ultraviolet, blue, green, yellow, red, cyan, magenta, infraredemission, or other wavelength, or a combination thereof.

A feature of the pattern can have a dimension of less than 10millimeters, less than 1 millimeter, less than 100 micrometers, or lessthan 1 micrometer. A feature of the pattern can have a dimension of atleast 1 centimeter, at least 10 centimeters, or at least 100centimeters.

The surface to which the semiconductor nanocrystals are applied istypically a substrate which includes one or more device layersin-between the substrate surface and patterned semiconductornanocrystals. Additional device layers are typically subsequentlydisposed over the nanocrystals. Individual saturated color LEDs can beformed at multiple locations on a single substrate to form a display.

For example, the substrate can include a layer including a holetransport material over the electrode. The method can include forming alayer including an electron transporting material over the nanomaterial.A second electrode can be applied over the layer including an electrontransporting material.

An embodiment of the invention including a dry transfer process of atleast the nanomaterials from the applicator to the device structure ispreferred when transferring semiconductor nanocrystals to an organiclayer of a light-emitting device structure during device fabrication.

When depositing semiconductor nanocrystals to an inorganic layer of alight-emitting device structure, the possible reaction of the liquid ofthe composition with the inorganic layer can be less of a concern.

In certain embodiments including semiconductor nanocrystals, thesemiconductor nanocrystals are deposited at a thickness of multiplemonolayers or less, e.g., greater than three monolayers, three or lessmonolayers, two or less monolayers, a single monolayer, a partialmonolayer, etc. The thickness of each deposited layer of semiconductornanocrystals may vary. Preferably, the variation of the thickness at anypoint of the deposited nanocrystals is less than three monolayers, morepreferably less than two monolayers, and most preferably less than onemonolayer.

In some applications, the substrate can include a backplane. Thebackplane includes active or passive electronics for controlling orswitching power to individual pixels. Including a backplane can beuseful for applications such as displays, sensors, or imagers. Inparticular, the backplane can be configured as an active matrix, passivematrix, fixed format, direct drive, or hybrid. The display can beconfigured for still images, moving images, or lighting. A lightingdisplay can provide white light, monochrome light, or color-tunablelight.

The deposition method is scalable, and can allow inexpensivemanufacturing of LEDs over a large surface area.

In certain embodiments, semiconductor nanocrystals are included in alight emitting device at a monolayer thickness. A monolayer can providethe beneficial light emission properties of semiconductor nanocrystalswhile minimizing the impact on electrical performance.

A light emitting device can include two layers separating two electrodesof the device. The material of one layer can be chosen based on thematerial's ability to transport holes, or the hole transporting layer(HTL). The material of the other layer can be chosen based on thematerial's ability to transport electrons, or the electron transportinglayer (ETL). The electron transporting layer typically includes anelectroluminescent layer. When a voltage is applied, one electrodeinjects holes (positive charge carriers) into the hole transportinglayer, while the other electrode injects electrons into the electrontransporting layer. The injected holes and electrons each migrate towardthe oppositely charged electrode. When an electron and hole localize onthe same molecule, an exciton is formed, which can recombine to emitlight.

When the electron and hole localize on a nanocrystal, emission can occurat an emission wavelength. The emission has a frequency that correspondsto the band gap of the quantum confined semiconductor material. The bandgap is a function of the size of the nanocrystal. Nanocrystals havingsmall diameters can have properties intermediate between molecular andbulk forms of matter. For example, nanocrystals based on semiconductormaterials having small diameters can exhibit quantum confinement of boththe electron and hole in all three dimensions, which leads to anincrease in the effective band gap of the material with decreasingcrystallite size. Consequently, both the optical absorption and emissionof nanocrystals shift to the blue, or to higher energies, as the size ofthe crystallites decreases.

The emission from the nanocrystal can be a narrow Gaussian emission bandthat can be tuned through the complete wavelength range of theultraviolet, visible, or infrared regions of the spectrum by varying thesize of the nanocrystal, the composition of the nanocrystal, or both.For example, CdSe can be tuned in the visible region and InAs can betuned in the infrared region. The narrow size distribution of apopulation of nanocrystals can result in emission of light in a narrowspectral range. The population can be monodisperse and can exhibit lessthan a 15% rms deviation in diameter of the nanocrystals, preferablyless than 10%, more preferably less than 5%. Spectral emissions in anarrow range of no greater than about 75 nm, preferably 60 nm, morepreferably 40 nm, and most preferably 30 nm full width at half max(FWHM) can be observed. The breadth of the emission decreases as thedispersity of nanocrystal diameters decreases. Semiconductornanocrystals can have high emission quantum efficiencies such as greaterthan 10%, 20%, 30%, 40%, 50%, 60%, 70%, or 80%.

A light emitting device can have a structure such as shown in FIG. 13,in which a first electrode 1302, a first layer 1303 in contact with theelectrode 1302, a second layer 1304 in contact with the layer 1303, anda second electrode 1305 in contact with the second layer 1304. Firstlayer 1303 can be a hole transporting layer and second layer 1304 can bean electron transporting layer. At least one layer can be non-polymeric.Alternatively, a separate emissive layer (not shown in FIG. 13) can beincluded between the hole transporting layer and the electrontransporting layer. One of the electrodes of the structure is in contactwith a substrate 1301. Each electrode can contact a power supply toprovide a voltage across the structure. Electroluminescence can beproduced by the emissive layer of the heterostructure when a voltage ofproper polarity is applied across the heterostructure. First layer 1303can include a plurality of semiconductor nanocrystals, for example, asubstantially monodisperse population of nanocrystals. Alternatively, aseparate emissive layer can include the plurality of nanocrystals. Incertain embodiments, a layer that includes semiconductor nanocrystals ispreferably a monolayer of nanocrystals.

The substrate 1301 can be opaque or transparent. The substrate can berigid or flexible. The substrate can be plastic, metal or glass. Thefirst electrode can be, for example, a high work function hole-injectingconductor, such as an indium tin oxide (ITO) layer. Other firstelectrode materials can include gallium indium tin oxide, zinc indiumtin oxide, titanium nitride, or polyaniline. The second electrode canbe, for example, a low work function (e.g., less than 4.0 eV),electron-injecting, metal, such as Al, Ba, Yb, Ca, a lithium-aluminumalloy (Li:Al), aluminum-lithium fluoride (Al:LiF), or a magnesium-silveralloy (Mg:Ag). The second electrode, such as Mg:Ag, can be covered withan opaque protective metal layer, for example, a layer of Ag forprotecting the cathode layer from atmospheric oxidation, or a relativelythin layer of substantially transparent ITO. The first electrode canhave a thickness of about 500 Angstroms to 4000 Angstroms. The firstlayer can have a thickness of about 50 Angstroms to about 1000Angstroms. The second layer can have a thickness of about 50 Angstromsto about 1000 Angstroms. The second electrode can have a thickness ofabout 50 Angstroms to greater than about 1000 Angstroms.

The electron transporting layer (ETL) can be a molecular matrix. Themolecular matrix can be non-polymeric. The molecular matrix can includea small molecule, for example, a metal complex. For example, the metalcomplex can be a metal complex of 8-hydroxyquinoline. The metal complexof 8-hydroxyquinoline can be an aluminum, gallium, indium, zinc ormagnesium complex, for example, aluminum tris(8-hydroxyquinoline)(Alq₃). Other classes of materials in the ETL can include metalthioxinoid compounds, oxadiazole metal chelates, triazoles,sexithiophene derivatives, pyrazine, and styrylanthracene derivatives.In certain embodiments,2,2′,2″-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi) canbe preferred. The hole transporting layer can include an organicchromophore. The organic chromophore can be a phenyl amine, such as, forexample,N,N′-diphenyl-N,N′-bis(3-methylphenyl)-(1,1′-biphenyl)-4,4′-diamine(TPD), 4-4′-N,N′-dicarbazolyl-biphenyl (CBP), 4,4-.bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPD), etc. In certainembodiments, N,N′-Bis(3-methylphenyl)-N,N′-bis-(phenyl)-spiro(spiro-TPD) can be preferred. The HTL can include a polyaniline, apolypyrrole, a poly(phenylene vinylene), copper phthalocyanine, anaromatic tertiary amine or polynuclear aromatic tertiary amine, a4,4′-bis(9-carbazolyl)-1,1′-biphenyl compound, or anN,N,N′,N′-tetraarylbenzidine.

The layers can be deposited on a surface of one of the electrodes byspin coating, dip coating, vapor deposition, or other thin filmdeposition methods. See, for example, M. C. Schlamp, et al., J. Appl.Phys., 82, 5837-5842, (1997); V. Santhanam, et al., Langmuir, 19,7881-7887, (2003); and X. Lin, et al., J. Phys. Chem. B, 105, 3353-3357,(2001), each of which is incorporated by reference in its entirety. Thesecond electrode can be sandwiched, sputtered, or evaporated onto theexposed surface of the solid layer. One or both of the electrodes can bepatterned. The electrodes of the device can be connected to a voltagesource by electrically conductive pathways. Upon application of thevoltage, light is generated from the device.

Preferably, semiconductor nanocrystals are processed in a controlled(oxygen-free and moisture-free) environment, preventing the quenching ofluminescent efficiency during the fabrication process.

Other multilayer structures may be used to improve the deviceperformance (see, for example, U.S. patent application Ser. Nos.10/400,907 and 10/400,908, filed Mar. 28, 2003, each of which isincorporated by reference in its entirety). A blocking layer, such as anelectron blocking layer (EBL), a hole blocking layer (HBL) or a hole andelectron blocking layer (eBL), can be introduced in the structure. Ablocking layer can include3-(4-biphenylyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole (TAZ),3,4,5-triphenyl-1,2,4-triazole,3,5-bis(4-tert-butylphenyl)-4-phenyl-1,2,4-triazole, bathocuproine(BCP), 4,4′,4″-tris{N-(3-methylphenyl)-N-phenylamino}triphenylamine(m-MTDATA), polyethylene dioxythiophene (PEDOT),1,3-bis(5-(4-diphenylamino)phenyl-1,3,4-oxadiazol-2-yl)benzene,2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole,1,3-bis[5-(4-(1,1-dimethylethyl)phenyl)-1,3,4-oxadiazol-2-yl]benzene,1,4-bis(5-(4-diphenyl-amino)phenyl-1,3,4-oxadiazol-2-yl)benzene, or1,3,5-tris[5-(4-(1,1-dimethylethyl)-phenyl)-1,3,4-oxadiazol-2-yl]benzene.A hole-injection layer (HIL) (e.g., Poly(3,4-ethylenedioxythiophene)poly(styrenesulfonate) (PEDOT PSS)) can optionally be introduced betweenthe first electrode and HTL.

An example of one embodiment of a device structure (from bottom to top)can include a 150 nm indium tin oxide (ITO) anode layer, a 70 nmPoly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) holeinjection layer (HIL), a 50 nmN,N′-Bis(3-methylphenyl)-N,N′-bis-(phenyl)-spiro (spiro-TPD) holetransport layer, a 5-10 nm semiconductor nanocrystal emissive layer, a50 nm 2,2′,2″-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole)(TPBi) hole-blocking/electron transporting layer and a 0.5 nm LiF/100 nmAl cathode layer. The ITO layer can be deposited, patterned and cleanedusing industry standard techniques. The PEDOT:PSS layer can be depositedby spin coating followed by bake out at 125 C for 20 minutes. All otherorganic and metal layers can be thermally evaporated in a high vacuumchamber. Prior to testing and operation the entire device is preferablyencapsulated using, for example, a sealant in a dry nitrogen environment(<1 ppm O₂, <1 ppm H₂O). A sealant of the type used in OLEDs is oneexample of a sealant that can be used.

Examples of semiconductor nanocrystals useful in the above describeddevice include, for example, and without limitation, those described inU.S. Patent Application Nos. 60/825,373, filed 12 Sep. 2006 and60/825,374, filed 12 Sep. 2006.

The performance of light emitting devices can be improved by increasingtheir efficiency, narrowing or broadening their emission spectra, orpolarizing their emission. See, for example, Bulovic et al.,Semiconductors and Semimetals 64, 255 (2000), Adachi et al., Appl. Phys.Lett. 78, 1622 (2001), Yamasaki et al., Appl. Phys. Lett. 76, 1243(2000), Dirr et al., Jpn. J. Appl. Phys. 37, 1457 (1998), and D'Andradeet al., MRS Fall Meeting, BB6.2 (2001), each of which is incorporatedherein by reference in its entirety. Nanocrystals can be included inefficient hybrid organic/inorganic light emitting devices.

The narrow FWHM of nanocrystals can result in saturated color emission.This can lead to efficient nanocrystal-light emitting devices even inthe red and blue parts of the visible spectrum, since in nanocrystalemitting devices no photons are lost to infrared and UV emission. Thebroadly tunable, saturated color emission over the entire visiblespectrum of a single material system is unmatched by any class oforganic chromophores (see, for example, Dabbousi et al., J. Phys. Chem.101, 9463 (1997), which is incorporated by reference in its entirety). Amonodisperse population of nanocrystals will emit light spanning anarrow range of wavelengths. A device including more than one size ofnanocrystal can emit light in more than one narrow range of wavelengths.The color of emitted light perceived by a viewer can be controlled byselecting appropriate combinations of nanocrystal sizes and materials inthe device. The degeneracy of the band edge energy levels ofnanocrystals facilitates capture and radiative recombination of allpossible excitons, whether generated by direct charge injection orenergy transfer. The maximum theoretical nanocrystal-light emittingdevice efficiencies are therefore comparable to the unity efficiency ofphosphorescent organic light emitting devices. The excited statelifetime (τ) of the nanocrystal is much shorter (τ˜10 ns) than a typicalphosphor (τ>0.5 μs), enabling nanocrystal-light emitting devices tooperate efficiently even at high current density.

Devices can be prepared that emit visible or infrared light. The sizeand material of a semiconductor nanocrystal can be selected such thatthe nanocrystal emits visible or infrared light of a selectedwavelength. The wavelength can be between 300 and 2,500 nm or greater,for instance between 300 and 400 nm, between 400 and 700 nm, between 700and 1100 nm, between 1100 and 2500 nm, or greater than 2500 nm.

Individual devices can be formed at multiple locations on a singlesubstrate to form a display. The display can include devices that emitat different wavelengths. By patterning the substrate with arrays ofdifferent color-emitting semiconductor nanocrystals, a display includingpixels of different colors can be formed.

Besides being useful to deposit nanomaterials in fabricating of displaydevices, methods in accordance with the invention can be used to depositvarious other materials, especially other materials comprisingnanoparticles, in fabricating a variety of lighting, electronic, oroptoelectronic devices.

For example, an unpatterned layer comprising nanomaterial comprising awhite light-emitting mixture of semiconductor nanocrystals can bedeposited onto a substrate by a method in accordance with the invention.The mixture includes semiconductor nanocrystals with different sizes andcompositions which can simultaneously emit light at differentwavelengths to achieve white light emission. The mixture ofsemiconductor nanocrystals are deposited as a layer in a devicestructure that also includes a hole transport layer and/or an electrontransport layer. The device may used to provide general lighting or maybe included in a display, e.g., a liquid crystal display, to providebacklighting. Alternatively, the device may further include a colorfilter to provide a full-color display. See U.S. Patent Application No.20060043361 entitled “White Light-Emitting Organic-Inorganic HybridElectroluminescence Device Comprising Semiconductor Nanocrystals”, ofLee et al., published 2 Mar. 2006, the disclosure of which is herebyincorporated herein by reference in its entirety.

Another example includes depositing nanomaterial comprising a pluralityof semiconductor nanocrystals by a method in accordance with theinvention in fabrication of a photodetector device or array ofphotodetector devices. A photodetector device includes one or morenanomaterials comprising a plurality of semiconductor nanocrystals whichare selected based upon absorption properties. When included in aphotodetector, semiconductor nanocrystals are engineered to produce apredetermined electrical response upon absorption of a particularwavelength, typically in the IR or MIR region of the spectrum. Examplesof photodetector devices including semiconductor nanocrystals aredescribed in “A Quantum Dot Heterojunction Photodetector” by AlexiCosmos Arango, Submitted to the Department of Electrical Engineering andComputer Science, in partial fulfillment of the requirements for thedegree of Masters of Science in Computer Science and Engineering at theMassachusetts Institute of Technology, February 2005, the disclosure ofwhich is hereby incorporated herein by reference in its entirety.

In one embodiment, a method of fabricating photodetector device includesapplying a layer including nanomaterial to an applicator from a transfersurface and depositing nanomaterial onto a substrate. In one embodiment,the nanomaterial including a plurality of semiconductor nanocrystals canbe deposited on the substrate as an unpatterned layer.

In another embodiment, a method of fabricating an array of photodetectordevices includes applying a layer comprising nanomaterial to anapplicator from a transfer surface and depositing nanomaterial onto asubstrate. In one embodiment, the nanomaterial including a plurality ofsemiconductor nanocrystals can be deposited on the substrate as apatterned layer. The substrate can further include an electrode. Asecond electrode can be deposited over the nanomaterial. Optionally, anelectron transport layer can be included between the nanomaterial andthe cathode electrode and/or a hole transport layer can be includedbetween the anode electrode and the nanomaterial.

A method of fabricating a photodetector device or array of devices canoptionally include depositing one or more nanomaterials in apredetermined arrangement (patterned or unpatterned). As discussedabove, nanomaterial can optionally be included in a composition.

Methods in accordance with the invention can also be used in depositionnanomaterials in the fabrication of memory devices. An example of anonvolatile device is described in U.S. patent application Ser. No.10/958,659, entitled “Non-Volatile Memory Device”, of Bawendi et al.,filed 6 Oct. 2004, the disclosure of which is hereby incorporated hereinby reference in its entirety. As discussed above, nanomaterial canoptionally be included in a composition.

Other techniques, methods and applications that may be useful with thepresent invention are described in, U.S. Provisional Patent Application60/792,084, of Maria J. Anc, for “Methods Of Depositing Material,Methods Of Making A Device, And System”, filed 14 Apr. 2006; U.S.Provisional Patent Application 60/792,086, of Marshall Cox, et al, for“Methods Of Depositing Nanomaterial & Methods Of Making A Device”, filedon 14 Apr. 2006, U.S. Provisional Patent Application 60/792,167 of SethCoe-Sullivan, et al, for “Articles For Depositing Materials, TransferSurfaces, And Methods”, filed on 14 Apr. 2006; U.S. Provisional PatentApplication No. 60/792,083 of LeeAnn Kim et al., for “Applicator ForDepositing Materials And Methods”, filed 14 Apr. 2006; and U.S.Provisional Patent Application No. 60/793,990 of LeeAnn Kim et al., for“Applicator For Depositing Materials And Methods”, filed 21 Apr. 2006;the disclosures of each of which is hereby incorporated herein byreference in its entirety.

As used herein, “top” and “bottom” are relative positional terms, basedupon a location from a reference point. For example, “top” of a devicestructure means farthest away from the substrate, while “bottom” meansclosest to the substrate. For example, for a light-emitting device thatoptionally includes two electrodes, the bottom electrode is theelectrode closest to the substrate, and is generally the first electrodefabricated; the top electrode is the electrode that is more remote fromthe substrate, on the top side of the light-emitting material. Thebottom electrode has two surfaces, a bottom surface closest to thesubstrate, and a top surface further away from the substrate. Where,e.g., a first layer is described as disposed or deposited “over” asecond layer, the first layer is disposed further away from substrate.There may be other layers between the first and second layer, unless itis otherwise specified. For example, a cathode may be described as“disposed over” an anode, even though there are various organic and/orinorganic layers in between.

As used herein, the singular forms “a”, “an” and “the” include pluralunless the context clearly dictates otherwise. Thus, for example,reference to an emissive material includes reference to one or more ofsuch materials.

When an amount, concentration, or other value or parameter is given aseither a range, preferred range, or a list of upper preferable valuesand lower preferable values, this is to be understood as specificallydisclosing all ranges formed from any pair of any upper range limit orpreferred value and any lower range limit or preferred value, regardlessof whether ranges are separately disclosed. Where a range of numericalvalues is recited herein, unless otherwise stated, the range is intendedto include the endpoints thereof, and all integers and fractions withinthe range. It is not intended that the scope of the invention be limitedto the specific values recited when defining a range.

In various instances herein, a semiconductor nanocrystal is referred toby the term “nanocrystal”.

It will be apparent to those skilled in the art that variousmodifications can be made in the methods, articles and systems of thepresent invention without departing from the spirit or scope of theinvention. Thus, it is intended that the present invention covermodifications and variations of this invention provided they come withinthe scope of the appended claims and their equivalents.

All the patents and publications mentioned above and throughout areincorporated in their entirety by reference herein.

Other embodiments of the present invention will be apparent to thoseskilled in the art from consideration of the present specification andpractice of the present invention disclosed herein. It is intended thatthe present specification and examples be considered as exemplary onlywith a true scope and spirit of the invention being indicated by thefollowing claims and equivalents thereof.

1. A method for depositing nanomaterial onto a substrate, the methodcomprising: applying a composition comprising nanomaterial to anapplicator surface from a transfer surface; and contacting theapplicator surface to the substrate.
 2. A method in accordance withclaim 1 wherein the composition further includes liquid.
 3. A method inaccordance with claim 2 wherein the composition is introduced to thetransfer surface by an inkcup.
 4. (canceled)
 5. (canceled)
 6. (canceled)7. A method in accordance with claim 1 wherein the transfer surfaceincludes one or more grooves.
 8. A method in accordance with claim 1wherein the transfer surface is smooth.
 9. A method in accordance withclaim 1 wherein the transfer surface is surface treated.
 10. A method inaccordance with claim 7 wherein the transfer surface is surface treated.11. A method in accordance with claim 10 wherein the surface treatmentwithin the one or more grooves is different from the surface treatmentoutside of the one or more grooves.
 12. A method in accordance withclaim 7 wherein the grooves are arranged to form a predetermined patterncomprising nanomaterial on the substrate.
 13. (canceled)
 14. A method inaccordance with claim 2 wherein the composition comprising nanomaterialis substantially free of liquid when applied to the applicator surface.15. A method in accordance with claim 1 wherein the compositioncomprising nanomaterial is substantially free of liquid when depositedonto the substrate.
 16. (canceled)
 17. (canceled)
 18. (canceled) 19.(canceled)
 20. (canceled)
 21. (canceled)
 22. (canceled)
 23. (canceled)24. (canceled)
 25. (canceled)
 26. (canceled)
 27. (canceled)
 28. A methodin accordance with claim 1 wherein the nanomaterial comprisessemiconductor nanocrystals.
 29. A method in accordance with claim 1wherein the nanomaterial comprises two or more different nanomaterials,wherein each nanomaterial comprises a plurality of semiconductornanocrystals.
 30. A method in accordance with claim 28 wherein thesemiconductor nanocrystals comprise a core/shell structure.
 31. A methodin accordance with claim 30 wherein the core comprises a Group Ivelement, a Group II-VI compound, a Group II-V compound, a Group III-VIcompound, a Group III-V compound, a Group IV-VI compound, a GroupI-III-VI compound, a Group II-IV-VI compound, a Group II-IV-V compound,alloys thereof, and/or mixtures thereof.
 32. A method in accordance withclaim 31 wherein the shell comprises a Group IV element, a Group II-VIcompound, a Group II-V compound, a Group III-VI compound, a Group III-Vcompound, a Group IV-VI compound, a Group I-III-VI compound, a GroupII-IV-VI compound, a Group II-IV-V compound, alloys thereof, and/ormixtures thereof.
 33. A method in accordance with claim 32 wherein thesemiconductor nanocrystals include at least one ligand attached to thesurface.
 34. (canceled)
 35. (canceled)
 36. (canceled)
 37. (canceled) 38.(canceled)
 39. (canceled)
 40. (canceled)
 41. (canceled)
 42. (canceled)43. A method of depositing nanomaterial onto a substrate, the methodcomprising: introducing a composition comprising nanomaterial and liquidonto a transfer surface; transferring at least a portion of thecomposition from the transfer surface onto an applicator; and depositingnanomaterial from the applicator onto the substrate after removal of atleast a portion of the liquid.
 44. A method of depositing nanomaterialonto a substrate, the method comprising: introducing a compositioncomprising nanomaterial and liquid onto a transfer surface; transferringat least a portion of the nanomaterial from the transfer surface onto anapplicator after removal of at least a portion of the liquid from thecomposition; and depositing nanomaterial from the applicator onto thesubstrate.
 45. A method for depositing nanomaterial onto a substrate,the method comprising: introducing a composition comprising thenanomaterial and a liquid onto a transfer surface; transferring thecomposition from the transfer surface onto an applicator; and depositingnanomaterial onto the substrate after evaporation of the liquid from theapplicator.
 46. (canceled)
 47. (canceled)
 48. A method of making a lightemitting device, comprising: applying a composition comprisingsemiconductor nanocrystals to an applicator surface from a transfersurface; and contacting the applicator surface to a substrate.
 49. Amethod in accordance with claim 48 wherein the substrate includes anelectrode, a hole transport material, an electron transport material, ahole injection material, an electron injection material, or acombination thereof.
 50. A method of forming a device comprising:applying a composition comprising nanomaterial on a surface of anapplicator from a transfer surface; contacting the surface of theapplicator to a substrate including a first electrode, therebytransferring at least a portion of nanomaterial of the composition ontothe substrate; and arranging a second electrode opposed to the firstelectrode.
 51. A method in accordance with claim 50 wherein apredetermined pattern comprising nanomaterial is transferred onto thesubstrate from the surface of the applicator.
 52. A method in accordancewith claim 50 wherein the nanomaterial includes a plurality ofsemiconductor nanocrystals.
 53. A method in accordance with claim 52wherein the plurality of semiconductor nanocrystals forms a layer on thesubstrate.
 54. A method in accordance with 53 wherein the layer is amultilayer of semiconductor nanocrystals.
 55. A method in accordancewith claim 53 wherein the layer is a monolayer of semiconductornanocrystals.
 56. A method in accordance with claim 53 wherein the layeris a partial monolayer of semiconductor nanocrystals.
 57. (canceled) 58.(canceled)
 59. (canceled)
 60. (canceled)
 61. A method in accordance withclaim 50 wherein the nanomaterial forms a pattern on the substrate. 62.(canceled)
 63. (canceled)
 64. (canceled)
 65. A method in accordance withclaim 50 further comprising applying a second composition comprisingnanomaterial on a surface of a second applicator from a second transfersurface; and contacting the surface of the second applicator to thesubstrate, thereby transferring at least a portion of the secondnanomaterial of the composition onto the substrate.
 66. A method inaccordance with claim 65 wherein the first nanomaterial and the secondnanomaterial each independently include a plurality of semiconductornanocrystals.
 67. A method in accordance with claim 66 wherein the firstplurality of semiconductor nanocrystals have an emission wavelengthdistinguishable from the second plurality of semiconductor nanocrystals.68. (canceled)
 69. (canceled)
 70. (canceled)
 71. (canceled) 72.(canceled)
 73. (canceled)
 74. (canceled)
 75. (canceled)
 76. (canceled)77. (canceled)
 78. (canceled)
 79. A method in accordance with claim 50wherein the substrate includes a layer including a hole transportmaterial over the first electrode.
 80. A method in accordance with claim79 further comprising forming a layer including an electron transportingmaterial over the nanomaterial.
 81. A method in accordance with claim 80wherein the second electrode is applied over the layer including theelectron transporting material.
 82. A method in accordance with claim 67further comprising applying a one or more additional compositionscomprising nanomaterial on a surface of a one or more additionalapplicators from one or more additional transfer surfaces, wherein eachadditional compositions is applied to a separate applicator from aseparate transfer surface; and contacting the surface of each one ormore additional applicators to the substrate, thereby transferring atleast a portion of the one or more additional compositions comprisingplurality of semiconductor nanocrystals onto the substrate. 83.(canceled)
 84. (canceled)
 85. (canceled)
 86. (canceled)
 87. (canceled)88. (canceled)
 89. An ink comprising nanomaterial dispersed in a liquid,wherein the ink has a viscosity of at least 0.1 cP.
 90. A compositioncomprising nanomaterial dispersed in a carrier medium, wherein thecomposition includes at least 0.1 mg semiconductor nanocrystals per mlcarrier medium.
 91. A composition in accordance with claim 90 whereinthe nanoparticles comprise semiconductor nanocrystal, a nanotube (suchas a single walled or multi-walled carbon nanotube), a nanowire, ananorod, a dendrimer, organic nanocrystal, organic small molecule, othernano-scale or micro-scale material or mixtures thereof.
 92. (canceled)93. (canceled)
 94. (canceled)
 95. (canceled)
 96. (canceled) 97.(canceled)
 98. (canceled)
 99. (canceled)
 100. A method for depositing ananomaterial onto a substrate, the method comprising: applying acomposition comprising nanomaterial to an applicator surface;positioning a mask including a predetermined pattern of aperturescomprising a predetermined shape and size on the substrate; andcontacting the applicator surface to the substrate through at least aone of the apertures.
 101. A method for depositing a nanomaterial onto asubstrate, the method comprising: applying a composition comprisingnanomaterial to an applicator surface from a transfer surface;positioning a mask including a predetermined pattern of aperturescomprising a predetermined shape and size on the substrate; andcontacting the applicator surface to the substrate through at least aone of the apertures.
 102. A method for depositing a nanomaterial onto asubstrate, the method comprising: applying a composition comprising apopulation of semiconductor nanocrystals to an applicator surface;positioning a mask including a predetermined pattern of aperturescomprising a predetermined shape and size on the substrate; andcontacting the applicator surface to the substrate through at least aone of the apertures.
 103. A method in accordance with claim 102 whereinthe population of semiconductor nanocrystals is applied to theapplicator surface from a transfer surface.
 104. A method in accordancewith claim 102 wherein the applicator including the population ofsemiconductor nanocrystals is dried prior to contacting the substrate.105. (canceled)
 106. A method in accordance with claim 102 wherein thesemiconductor nanocrystals comprise a core/shell structure.
 107. Amethod in accordance with claim 102 wherein the semiconductornanocrystals comprise a core/shell structure, wherein the core comprisesa Group IV element, a Group II-VI compound, a Group II-V compound, aGroup III-VI compound, a Group III-V compound, a Group IV-VI compound, aGroup I-III-VI compound, a Group II-IV-VI compound, a Group II-IV-Vcompound, alloys thereof and/or mixtures thereof.
 108. A method inaccordance with claim 102 wherein the semiconductor nanocrystalscomprise a core/shell structure, wherein the shell comprises a Group IVelement, a Group II-VI compound, a Group II-V compound, a Group III-VIcompound, a Group III-V compound, a Group IV-VI compound, a GroupI-III-VI compound, a Group II-IV-VI compound, a Group II-IV-V compound,alloys thereof and/or mixtures thereof.
 109. A method in accordance withclaim 102 wherein the semiconductor nanocrystals include at least oneligand attached to the surface.
 110. A method in accordance with claim102 wherein the mask comprises a polyimide film, a fluorinated polyimidefilm, or a film including a fluorinated polyimide coating on at leastone surface thereof.
 111. A method in accordance with claim 108 whereinthe semiconductor nanocrystals include at least one ligand attached tothe surface.
 112. A method in accordance with claim 1 wherein thetransfer surface is a cliché.
 113. A method in accordance with claim 1wherein the transfer surface is silanized.
 114. (canceled) 115.(canceled)
 116. (canceled)
 117. (canceled)
 118. (canceled)
 119. Anapplicator made from a material comprising a silicon based elastomerdoped with a fluorinated polymer.
 120. An application in accordance withclaim 119 wherein the fluorinated polymer is included the material in anamount of at least about 0.001 weight percent.
 121. An application inaccordance with claim 119 wherein the fluorinated polymer is includedthe material in an amount of at least about 0.001 weight percent up toan amount that is less than the amount at which the silicon basedelastomer including the fluorinated polymer dopant cannot be cured. 122.An application in accordance with claim 119 wherein the fluorinatedpolymer is included the material in an amount greater than zero up to atleast about 0.1 weight percent.
 123. An applicator in accordance withclaim 119 wherein the fluorinated polymer comprises a fluorinatedpolysiloxane.
 124. An applicator in accordance with claim 119 whereinthe fluorinated polymer comprises a fluorinated polysiloxane. 125.(canceled)
 126. (canceled)
 127. (canceled)
 128. (canceled) 129.(canceled)
 130. (canceled)